FIRE BUNKERS - iPrimus
EVOLVING DRAFT - 28/5/2009 edition.
Fire Bunkers
A resource document covering:
• Whether or not to have a Fire Bunker;
• Design and Location considerations; &
• Other things to consider.
This a single Word document, not a series of Web pages because:
• the decisions you make are important and may be expensive
• you really need to read it all, even if you choose to ignore / discard some of it
You need to be in Print Layout view to see all graphics in this document. Go View, Print Layout
This an evolving document. If you are reading a paper or saved copy and the date on the top right of this page is not current, get the latest copy from:
FEEDBACK AND SUGGESTIONS WELCOMED. Please send to: ianpullar@
PLEASE PASS THIS ARTICLE ON. If you know individuals or groups who may be interested in this article, or could contribute to its improvement, please email this link to them.
IMPORTANT - The author does not claim to be an expert – simply a person who has done research and thought about some ideas which are yet to be tested, and which may or may not work. You need to get your own information and make your own decisions.
BEFORE YOU PRINT IT - please note there are lots of pages.
For an overview of the Black Saturday bushfires, see
This project has no association with any commercial venture.
Cheers – Ian Pullar ianpullar@
DOCUMENT CONTROL / CHANGES (Thanks for your contributions)
|7/3/2009 |First release |
|17-27/3/2009 |Numerous updates throughout. Suggest you consider re-reading it now. |
|29/3/2009 |Addition of – things to do when you need to use your bunker – your “fire bunker plan”. |
|30/3/2009 |Addition of – Other products and useful equipment links and new supplier/service provider |
|7/4/2009 |New supplier of flat pack fire bunkers; |
|8 & 9/4/2009 |Addition of – 10/2005 Vic Office of Emergency Services Position Paper on [public] fire refuges Good reading. Interestingly, |
| |some of the experiences of Black Saturday make some of the info seem obsolete. Also interesting that some info is SO hard to|
| |find, which is why I wrote this paper! Signage info updated. New link re soil as a barrier added. |
|14/4/2009 |Addition of – Alliance for Fire and Smoke Containment (PFPA) info / links and in doors section of this paper. LOTS of info |
| |via this site. |
|2/5/2009 |Addition of – Wildfire Protection Services bunker, and an absolutely EXCELLENT article from The Age on getting over |
| |bushfires. Click here for full article. |
|14/5/2009 |Addition of – further supplier Bushbunker - solid purpose built unit with accessories built in |
|22/5/2009 |Addition of – Why Black Saturday fires were so hot, 80% of damage is with south west change & CFA Woollen Fire Blankets |
| |source |
|23/5/2009 |Addition of – Bunker Building Stories (Please send me more!) Thanks to Diederik |
|28/5/2009 |Addition of – Survival in a Fire Bunker – transcript from Royal Commission |
| |Update to Oxygen / Air Supply Tanks & Compressors |
| |Increasing strengthening for block bunkers and bunker roofs (various places in document). |
INDEX - CLICK ON RELEVANT LINE TO GO STRAIGHT TO PAGE
PURPOSE OF WRITING THIS 4
WHY A FIRE BUNKER? 4
RECENT LESSONS 5
BUNKER SURVIVAL STORIES 5
YOU’RE INTERESTED IN BUILDING A FIRE BUNKER - WHAT TO DO NOW? 6
READING MATERIALS CURRENTLY AVAILABLE 7
DANGERS 8
WHY THE DISCLAIMER? 8
DESIGN CONSIDERATIONS 9
DUAL USE vs MAIN PURPOSE and 9
LOCKED vs UNLOCKED 9
WHEN WILL IT BE USED? 10
HOW LONG AFTER THE FIRE WILL IT NEED TO BE USED FOR? 11
BUILD IT UNDER THE HOUSE? 11
SIZE 11
ENTRANCES / DOORS 12
FIRE DOORS, DOOR JAMBS (IE SURROUNDS) and DOOR SEALS 13
THE IMPORTANCE OF DOOR MAINTENANCE 14
DOOR LATCHES 14
AN ALTERNATIVE TO DOORS IN JAMBS/SURROUNDS 14
MORE THAN ONE ENTRANCE 15
PROTECTION FROM ENTRANCE/S AGAINST FALLING TREES, BRANCHES ETC. 15
WINDOWS 15
VENTILATION 15
FAN FORCED VENTILATION UNITS 16
SPECIAL REQUIREMENTS FOR PETS 18
DESIGN FOR LATER EXPANSION? 18
LOCATION – WHERE SHOULD YOUR BUNKER BE BUILT? 19
CONSTRUCTION MATERIALS AND METHODS 20
ABOVE GROUND, IN-GROUND, TOP DOOR OR SIDE DOOR/S? 21
HOW FIRE-PROOF DO I HAVE TO MAKE IT? 22
WHAT ABOUT A BURIED STEEL CONTAINER? 24
THE USE OF SOIL AS A BARRIER 24
DRAINAGE 24
POTENTIAL FOR GROUND SLIPPAGE / COLLAPSE and EROSION 25
MOULD AND MICROBES 25
SPIDERS AND BUGS 25
SOIL TYPES 26
POWER AND LIGHTING 26
FLOORING AND FLOOR COVERINGS 27
DÉCOR 27
BUNKERS AND CHILDREN 27
BENCHES, SHELVES AND HOOKS 28
COMMUNICATIONS 28
SIGNAGE 29
MAKING YOUR FIRE BUNKER BLEND IN / LOOK GOOD. 29
OXYGEN / AIR SUPPLY TANKS & COMPRESSORS 29
COUNCIL PERMITS – AND THE RAMIFICATIONS OF IGNORING THEM 31
ONE DIY FIRE BUNKER BUILDER’S EXPERIENCE WITH COUNCIL 32
LIABILITY AND INSURANCE ISSUES 32
BUILDERS 32
WARRANTIES 33
THE IMPORTANCE OF ADEQUATE INSURANCE ON YOUR HOUSE & OTHER ASSETS 33
COSTS and TIME 33
MAINTENANCE 33
THINGS YOU MAY WISH TO PUT IN YOUR BUNKER TO BE FULLY PREPARED 34
THINGS YOU SHOULD LEAVE OUT OF YOUR BUNKER 36
THINGS YOU SHOULD NOT DO IN YOUR BUNKER 36
PREPARATION FOR BUNKER USE – YOUR FIRE BUNKER PLAN 36
WHAT TO DO BEFORE YOU HEAD INTO YOUR BUNKER 36
WHAT TO DO AS YOU HEAD INTO YOUR BUNKER 37
AFTER THE FIRE HAS PASSED 38
CLOTHING 38
IF YOU THINK THE RULES NEED TO BE CHANGED, OR MORE RESEARCH IS REQUIRED– DO SOMETHING ABOUT IT 39
BUNKER BUILDING STORIES 40
LINKS 40
New building codes 41
NEWS ARTICLES 42
BUSHFIRE TALK 42
COMMERCIAL BUNKERS AVAILABLE FOR SALE 42
OTHER PRODUCTS & USEFUL EQUIPMENT LINKS 45
SAMPLE DESIGN, WITH 2 DOORS AND PROTECTED ENTRANCES 47
ROOFING - POSSIBLE CONSTRUCTION METHOD. 48
ROOFING – CONSTRUCTION METHOD IF TWO WALLS 49
DIAGRAM OF SAME STRUCTURE WITH LOCKABLE STORAGE AREA FOR WINE OR OTHER ITEMS. 50
EXAMPLE OF MODIFIED CONCRETE TANK. 51
BEST POSITION ON THE SITE (also see next page) 52
BEST POSITION ON THE SITE (continued). 53
LOW VOLTAGE VENTILATION SYSTEM 54
SIGNS 55
THE HIDDEN IMPACTS OF BUSHFIRES 56
EQUIPMENT AND OTHER HELPFUL STUFF 56
THAT’S IT. 57
AGE ARTICLE 59
FIRE BUNKERS
PURPOSE OF WRITING THIS
I started doing some research on fire bunkers for a relative who lives in the country and it soon become apparent that there was a lack of information published on the subject which was collected in one place. So, I started collecting all the information I could find – and hoped that others would contribute their collective experience, knowledge and wisdom. That process has not yet been completed and that’s why this is an evolving draft.
I am aware there are folk screaming out for fire bunkers, but it is really important that they get it right. I am also aware that there is most likely to be work on this subject initiated by the authorities in the coming months, and so this document must only be considered “food for thought”.
The Victorian Government has initiated a Royal Commission to look into the fires, and presumably fire bunkers will be one of the things being looked at. However the full report of this Commission is not expected until just before next bushfire season. The new building regulations for HOUSES are now released, but do not cover fire bunkers. It is not known how long after the Royal Commission report that any new building standards for FIRE BUNKERS might be available.
The purpose of this early material is therefore to give you that initial food for thought regarding:
• whether or not have a fire bunker;
• design and location considerations; and
• other stuff to consider.
The intention is that this article will be updated as suggested improvements are received. However it is also intended that it retain its aim to be food for thought for your basic bunker, not something which is complex and would fall into the category of a major project.
WHY A FIRE BUNKER?
So that IF you / your family / friends have been unable to evacuate safely and are caught in a bushfire or firestorm it can:
• protect you from
o radiant heat;
o super-heated air;
o loss of oxygen;
o falling embers, branches, trees etc.
• provide a place to assemble people and their requirements before the fire;
• reduce your reliance on luck;
• provide storage of a small volume of provisions/tools; and
• provide a safe haven for immediately after the fire.
IMPORTANT – a fire-bunker is not a replacement for sensible risk-management, including appropriate evacuation well before the fire arrives.
RECENT LESSONS
The recent (2/09) fires in Victoria have highlighted a number of things.
Some folk were prepared for bushfires, but almost none were prepared for fire-storms, which are generally much hotter and move faster.
In bushfires, there was a generally accepted concept that if you fought to save your house, and then retreated to within your house if and when required by the heat, you could continue your fire fighting efforts inside – and if you were not successful you could escape outside because by then the main heat of the fire would have passed. This worked much of the time but as fatalities still occurred, it obviously didn’t work all of the time.
Listening to the Royal Commission (live on the Web, ) I heard Dr Kevin Tolhurst explain that normally the fuel load and kindling had to be "pre-dried" first by the flames before the fire could ignite it. The energy required by the fire doing this, quelled it down to the types of fires of the past. But on days of temperatures in the 40s before Black Saturday, the fuel was pre-dried meaning there was no moisture to quell any of the energy – so it was up to furnace temperatures and caused instant ignition and rapid spread of the fire front and fast spotting from embers. The combination of the wind PLUS this pre-drying caused unprecedented conditions.
You can read the transcript at: . Start at page 986, which is page 30 of the PDF file.
Surviving bushfires was a mixture of:
• preparation; and
• having not too much bad luck.
However in the fire-storms of Black Saturday the heat was so intense that houses exploded into flames before it was safe to go outside.
Many folk had almost no warning whatsoever of the fires, or allowed too little time to leave the area and had nowhere to go.
Surviving the fire-storms of Black Saturday was a mixture of:
• (for some folk) preparation; and
• (for many folk) an absolutely remarkable amount of good luck.
A very small number had protection from the heat, in purpose-built shelters or shelters which had features similar to a purpose-built fire bunker. There are many lessons to be learned from this.
BUNKER SURVIVAL STORIES
The Bushfires Royal Commission transcripts contain a blow by blow description of a family’s experience leading up to the bushfire and their retreat to their bunker. See: . It begins on page 1491, which is page 104 0f the PDF file.
Brief report from The Age is contained at
This bunker, built beside a water tank, saved 3 lives. The story below is from The Age newspaper.
[pic]
When Ms Berry was seven months' pregnant, she started to nag her husband to build a fire bunker behind the water tank, worried the sprinklers would not do enough to protect their timber home on Bald Spur Road in a fire.
"I said 'stop nagging, I'll build the bloody thing,' " says her husband, Andrew Berry, the owner of M Cafe.
The bunker, dug into an earth embankment with 15-centimetre concrete walls and a $1000 fireproof door, saved the life of the couple and their son Raphael, 14 months old.
"It was like a firestorm, it was like a raging inferno. It's a cliché, but that is what it was like," Ms Berry says.
When the flames engulfed their home, they wrapped themselves in wet towels and sprinted to the bunker. Miraculously, Ms Berry's bare feet were not burned.
"We couldn't shut the door of the bunker, it was that buckled and warped," Mr Berry says. The embers were coming through the gap, it was like the fire was coming to get us."
If there is a lesson to be learned, Mr Berry believes it is the importance of being prepared and taking responsibility for the safety of your family.
"We had the biggest slap-in-the-face warning when the fire came through here three to four years ago," he says.
"We did something about it and walked out of the street alive."
YOU’RE INTERESTED IN BUILDING A FIRE BUNKER - WHAT TO DO NOW?
There are various scenarios for people wishing to build a fire bunker.
• Some folk will start too soon, and possibly without council approval, and find they could have done it better or easier, or they’ll have a non-complying bunker which is possibly unsafe and/or may have to be removed.
• Some will start at the right time and get just what they want.
• Some will leave it too late and not be able to get their bunker installed before next bushfire season.
• Some will wait until more testing type work has been done and may then build an excellent bunker in accordance with the new specifications. This may or may not be completed before next bushfire season.
I can’t tell you what to do, there are all your own decisions.
If you do choose to install a fire bunker, your choices will be:
• to have one built to your specifications; or
• to install a commercially made prefabricated model. There are links to some suppliers in this document.
However – whilst risks can be reduced with preparation and a well designed and constructed bunker, never underestimate the advantages of simply being away from the area well before the fire arrives.
This consistent message is also in many of the websites of the commercial suppliers – that a bunker is a place of last resort and not to be treated as an alternative to evacuating the area early and safely.
A FIRE BUNKER DOES NOT PROVIDE A GUARANTEE OF SAFETY.
A safe family is far more important
than putting lives at risk
attempting to save a building or other asset.
READING MATERIALS CURRENTLY AVAILABLE
At time of writing, there appeared to be very little information collected in ONE PLACE covering all things that need to be taken onto account.
The following extracts from the CSIRO’s website show the current state of research (or lack of it in relation to fire bunkers using modern materials) and also provides some good food for thought.
“What research has CSIRO done on fire bunkers?
CSIRO is not currently conducting research into bushfire bunkers or shelters. Previous research by the Department of Defence indicated that underground bunkers may not be safe in bushfires due to the accumulation of toxic gases coming from a bushfire itself. … The use, design and efficacy of current era bunkers has not been investigated by CSIRO. (My emphasis added.)
As with any form of bushfire refuge, bushfire bunkers must be assessed in an overall context taking into consideration issues such as:
• expected bushfire behaviour
• design and construction criteria
• preparation and maintenance
• intended and probable use of the bunker
• establishing a safe path to the bunker.
As well as the technical issues, there are a range of other considerations including:
• decision making processes and education around when to retreat to the bunker
• when to close off a bunker
• how long to remain in the bunker
• how to determine when it is safe to exit the bunker.”
Link to the relevant page is:
South Australian Country Fire Service (CFS) have a position paper on Bushfire Shelters and Bunkers. In short, they note an absence of Australian Standards an are not currently encouraging these structures. See the last item (item 29) on web page
DANGERS
BUNKERS BRING SOME PROBLEMS OF THEIR OWN. The CSIRO has noted problems in the past with smoke and toxic gasses, and also notes “other considerations”, including education in how they should be used.
In short – there are dangers to the community at large if they are about, and there are other dangers if they are not.
Having a room without light or ventilation could be dangerous on all days of the year for children or others who might lock themselves in.
A fire bunker which has building faults, initially or down the track, could be a potential death-trap in a fire, and simply evacuating early could prevent a tragedy.
The safest place to be when a fire is about is well away from it. Hence the many recommendations about that you evacuate – and early. Immediately post the Black Saturday fires, many people heeded such warnings. Having a fire bunker might make some folk ignore the fire danger all together.
Against all that, folk do not always have that luxury of evacuating, because of late notification, an error of judgement, escape routes cut off, lack of transport, or just bad luck. So the appropriateness of fire bunkers may need to be considered for when you are unable to remove yourself from the area.
WHY THE DISCLAIMER?
The disclaimer is because you need to get your own information and make your own decisions. The author does not claim to be an expert – simply a person who is doing research, has thought about some ideas which are yet to be tested, and which may or may not work.
Essentially, to rely on such a structure is to put your life and the lives of others at risk. This includes the lives of fire fighters who put themselves in danger to make you safe.
The disclaimer (repeated at the bottom of each page) is so you recognise that your choices and actions are your responsibility, not the author/s’. (Ie don’t sue me.)
DESIGN CONSIDERATIONS
DUAL USE vs MAIN PURPOSE and
LOCKED vs UNLOCKED
Compromising the structure’s
main purpose will usually
compromise its ability to do its job.
To avoid loss of effectiveness for providing safe haven in a fire, the focus needs to remain on the requirements for it achieving this main purpose.
It is possible to come up with numerous “dual uses” for your fire bunker, and at first thought this might appear a way of justifying the cost and space. However:
• its secondary use will usually compromise its primary use as a fire bunker; and
• the requirements of a fire bunker will usually compromise its secondary use.
For example, the requirements for a fire bunker to
• have special entry requirements;
• be totally and quickly sealable;
• be clear of junk to trip over and hazardous materials;
• be appropriately located clear of other structures and trees;
• be insulated from immense heat; and
• always be unlocked / accessible
compromise its ability for many other uses.
Further, to build a bunker big enough to accommodate many dual uses is most likely to cost far more than to build two separate structures – eg. (a) an effective bunker with the features mentioned above and (b) a simpler purpose-built shed for your proposed secondary purpose (complete with wide doors, ventilation, power, lighting, windows etc).
For the reasons above, this article focuses on a simple bunker.
If you do decide to go down the dual use path, consider carefully how you will achieve all your objectives.
Regarding locks, the importance of accessibility cannot be over-stated. All those stories in the B-grade disaster movies actually do happen. I was reading a report from someone who was protecting his house from the inside, went out the back for a moment and locked himself out. He then had to run the gauntlet of the flames to get in the front door.
Consider that a misplaced or dropped key could cost you and your family your lives, and also remember it may be a young family member who suddenly needs access in your absence.
If you intend it having a dual use as a wine cellar, which may work well, for reasons of safety ensure that:
• your wine bottles are stored in such away that they will not fall, break and be a safety hazard;
• if you need them to be locked up, simply have them locked in a cage in the structure, but make sure there is still room for the main purpose;
• do NOT lock the door/s of the bunker itself.
• don’t allow your growing collection to compromise the safety of your haven.
In the design phase, consider how much room you require for your wine cellar, and how you might lock it up with cage doors if you require this.
For storing other valuables (eg duplicate copies of identity documents, bank account and details of your house and car insurances, internet provider account, mobile phone etc and possibly extra copies of important photos) consider a securely attached locked box or safe, with all documents double wrapped in plastic, or simply having copies securely stored at another family member’s house.
KISS = Keep It Strictly Simple
WHEN WILL IT BE USED?
It is envisaged that your fire bunker will be used:
• as a place to take children and others who might require protection early (if you have not evacuated well before the fire has arrived). Note that children must NOT be left alone in these circumstances;
• similarly for pets;
• as a place to retreat to for safety when you wish to retreat from the fire;
Where fire may possibly be expected in the night, you may want to all bunker down in it overnight. So you may choose to add some basic comforts such as benches, folding chairs and mats to sleep on.
To ensure there is sufficient air, it is VITAL that the doors and vents are left open until they need to be closed to protect you all from the fire.
It might also be required as a place to give you shelter well after the main fire has passed, as your house and transport may not be usable after the fire, and others about may be too busy or not available to transport you from the area. Accordingly, you may wish to consider the things you might take into the bunker (there is a list of suggestions later).
This will also get you thinking on the extra space you will need to accommodate all of this.
If you lose your home to the fire, it is not envisaged that your bunker be your “first home” immediately after the fire, as it is anticipated you would get yourself an alternative temporary structure (eg a caravan or a temporary building) which is not restricted by the design elements essential for a safe bunker.
HOW LONG AFTER THE FIRE WILL IT NEED TO BE USED FOR?
There is a lot of material suggesting the main fire front will be gone in 10 to 15 minutes. However there are many stories from survivors who said it was not safe to come out for 40 minutes to two hours, and some who said the danger did not fully pass for several hours. However that does not mean the door would have to stay closed for that long, PROVIDED the entrances are protected from the radiant heat
It really depends on the day, the nature of the fire, the local geography and the combustible materials around you.
With children, it may not be safe at all in the fire area, even well after the fire has passed, and they should be kept in the (now opened) bunker until they can be safely evacuated.
There may be dangers from falling tree branches or other debris, or rain may make there area extremely uncomfortable if not dangerous.
There have been many instances of pets being let loose early and having their paws burned by the hot ground or hot coals.
BUILD IT UNDER THE HOUSE?
Generally, this is regarded as unsafe unless (a) it is really very well designed and constructed and (b) you have a lot of luck on your side in the event of a fire.
• The structure itself will require extra heat-proofing to protect it from the house above which may collapse on it and may burn for some time.
• Entry / exit to the fire bunker may be severely compromised if there is a structural failure/collapse of the main dwelling and also from the heat of the burning building.
• You will need to have it all approved as part of your house-building permit.
SIZE
You can buy basic units, but you may want something with a bit more space and functionality.
It needs to be big enough to:
• hold all the people who might need to use it;
• have enough air-space so you don’t run out of oxygen;
• keep the gear (if any) that you intend to keep in it;
• keep all the “last minute” gear (if any) you may wish to take in; and
• accommodate any dual use purpose (including potential expansion of same).
You may also want it to be big enough to:
• bunker down overnight if there is a high fire risk, particularly of children are involved, ditto pets;
• take in some basic “re-starting” stuff in there for when the fire has passed and you might not have a house or car; and
• have some basic fire fighting equipment in with you, as buildings which are not burned in the main fire often burn later because of smouldering embers being blown about. With equipment outside possibly being damaged or destroyed in the fire, you may need access to hoses, hose fittings, buckets, mops and rakes to protect your buildings post-fire.
However be aware that all the stuff you might like to take in may take up valuable air space, so make sure it is big and roomy enough to accommodate you needs and still allow plenty of free cubic metres for you to move about freely. (At this stage I am not aware how much air space is required per person for a (say) a 60 minute stay without additional ventilation.)
Constraints upon you making a large bunker may include:
• cost;
• available space on site, and site layout;
• aesthetics;
Minimum height will be dictated by the height of your fireproof doors PLUS their surrounds.
The standard door height is usually 2040mm (6 foot 8 inches).
Eleven 200mm blocks high will make it 2200mm (ie 2.2 metres or 7 foot, 2½ inches)
ENTRANCES / DOORS
To ensure;
• safety of occupants when door is opened
• the door cannot be warped or damaged by heat
• minimisation of smoke and flame entry
the doors must NOT be directly exposed to outside.
This means an offset door via a perpendicular “corridor” into your bunker.
The entry should also be well clear of potential sources of radiant heat and other hazards.
• Doorways must be designed so a warping of the door or door surround (as may occur if a nearby falling tree upsets the structure) will not cause the door to be jammed shut or be unable to be closed.
• Latches must be able to ensure sealing of the door, but must be simple so as to not break or jam
• Doors MUST be inward opening, so there is nothing to stop them being opened when required.
The exception to this inward opening door arrangement is that if you have TWO doors, you might choose to have one opening inward and the other outward. The reasoning being that if the doors jamb because they have expanded in the winter and you have not maintained them, at least you can push hard against the door opening outwards.
• Ensure both doors have VERY SOLID and VERY WELL ATTACHED HANDLES for pulling them closed/open, IN ADDITION TO the standard latch handle. The last thing you would want is for your handle to fall off, so you’ll possibly require fixing to go right through the door.
FIRE DOORS, DOOR JAMBS (IE SURROUNDS) and DOOR SEALS
Fire doors are readily available commercially. These provide a “fire rating” of 2 to 4 hours however be aware that this may be affected by:
• the intensity of the fire – the Black Saturday fires were hot enough to melt aluminium engine blocks; and
• the placement of the doors – whether or not placed directly exposed to the fire (hence the suggestion that the entry “corridor” protect the door from direct exposure).
For info about fire ratings, see
Retailers of these doors can also provide door jambs/surrounds and seals that mount in them. Expect to pay around $1500 for each door / surround / seal set. They can also provide suitable door latches.
Door jambs (ie metal door surrounds) will come in THREE sides (ie top, and two sides) or FOUR sides (ie top, bottom, and left and right).
Because of the lip, the FOUR sided door frame is a slight trip hazard, but the extra sealing at the bottom means it is less of a SMOKE HAZARD. Also, this might stop easy hosing out of your bunker, but this might possibly be overcome by the manner in which you arrange your drainage mechanisms.
Remember that door jambs will need to be ordered left-hand or right-hand, and will need to be installed with the bricks. See , or if that link does not work, click on the Download Build-02 Building in Masonry walls tech sheet (pdf) line on .
Check to see whether you will need to do anything special in the laying of your slab if you are using metal doorframes, particularly the four sided doorframes.
For some detailed info on fire doors and fire door hardware, see
THE IMPORTANCE OF DOOR MAINTENANCE
One bunker owner discovered on entering on Black Saturday that he had not maintained his door, and it had expanded over the winter because of the moisture and would not close within the frame. He and his family survived, but a bit or maintenance would have reduced some of the trauma.
If your door expands take it off, plane down the sides as required. You may have to plane down the side with the hinges, as the latch/handle does not lend itself to being moved. Seal the planed edge with quality paint (water-based) and reinstall the door.
DOOR LATCHES
Door latches MUST be able to be opened from BOTH the inside and outside, so it is NOT possible to lock anyone IN or OUT – including when the bunker is not intended to be in use.
UNDER NO CIRCUMSTANCES put a “padbolt” or other similar sliding bolt or latch on a fire door that can only be opened on one side.
Be aware that your fire door may not have seals at its base. Whether or not it does, you will need to make sure you have in your bunker towels, and water to wet them with, to seal the base of the door if required.
Fire Door suppliers can supply latches/handles which have already been approved for such purposes, but you are again reminded that these will remain more reliable if not exposed to radiant heat.
NEVER put your unexposed skin on a handle that may have been heated from the other side.
Store a jemmy bar in your bunker for the unlikely event of the door/s jamming.
AN ALTERNATIVE TO DOORS IN JAMBS/SURROUNDS
Doors in your house normally fit neatly within a door frame. This makes a good enough seal in a normal domestic setting. As shown in the illustrations a couple of sections above, fire door frames can include neoprene seals to improve this sealing.
An alternative to having the door IN the frame is to have the door AGAINST the frame, like a fridge door pushes up against the fridge.
DOOR IN DOOR FRAME (Like a normal house door)
|Advantages |Disadvantages |
|Easy to get – buy set up from manufacturer |If structure moves, door can get caught in door frame. |
|Can include commercially available seals |If door not maintained and swells or warps, could get stuck in frame or might |
|Latching devices commercially available |not close. |
DOOR AGAINST DOOR FRAME (Like a fridge door)
|Advantages |Disadvantages |
|Can maintain seal even if door-frame moves or door expands |Special seals and seal attaching may be required |
|slightly |Special latching and hinging required |
| |Accuracy of latch and hinge alignment is critical to ensure sealing |
| | |
MORE THAN ONE ENTRANCE
Having only one entrance makes the structure “single point sensitive”, ie if one thing bad happens there might be no way to get on or out.
Having two entrances also allows some airflow for ventilation when it is not in use (if doors are left open), which will reduce accumulation of damp and mould.
PROTECTION FROM ENTRANCE/S AGAINST FALLING TREES, BRANCHES ETC.
This may be particularly important if you only have one entrance. You can arrange heavy steel protection bars or similar to reduce this risk. However be aware that a falling tree may weigh many tonnes, so dual entrances are recommended.
WINDOWS
Windows do not fit well with fire bunkers because:
• unless built to very high standards, they do not have the same fire-proof ratings as bricks; and
• clear glass does not stop radiant heat.
VENTILATION
There are differing schools of thought regarding vents. One website states “Vents will simply allow air to escape rapidly when the fire front is upon you, and then the shelter will “breathe in” drawing smoke and heat into the shelter. Poorly placed synthetic filters can melt at this point and poison the occupants with toxic fumes. US research suggests air self sufficiency through the period of danger is a safer strategy.” (See suppliers links section for source.)
The other school of thought is that there is a year round danger of suffocation, ie without there even being a fire about. To reduce that risk, openable vents are a must.
Vents:
• need to be fireproof, and not compromise the structure of the integrity of the door or wall in which they are mounted;
• must not transmit heat into the bunker, as might occur if the vent was made with a single layer of steel;
• must normally be left in the open position;
• need to be out of reach of young children;
• must be able to be closed and sealed tight from INSIDE the bunker. This will require them to have a screwing or latching mechanism which ensures the seal remains effective and that they cannot be blown open by wind or air pressure; and
• be facing into the safety of the inner corridor and NOT be facing the outside where they may be exposed to radiant heat.
It is also recommended that vents be bird-proof and bug proof. You may wish to keep the vents normally open and will not want birds entering and fouling your shelter, or to die in there, which would be both a shame for the birds, and a potentially severe health risk for humans. Simple wire bird netting on the outside can achieve this.
Similarly, you do not want bugs to crawl in, particularly if they intend to raise a family in there. You really don’t want to be heading in and discover a bee or wasp nest in there. Aluminium flywire should do the trick.
If your vent is a pipe, use the bird and bug netting at BOTH ends of it.
When do you close the vents?
You are probably best to close the vents (as these could be fiddly) before you need to retreat to your bunker, but leave the doors open until it is obvious you need to close them. Vents must be closed and sealed when the fire arrives.
When do you open the vents/door?
After the main fire front has passed (reports suggest this may be greater than 10 to 20 minutes), it might be appropriate to have a look outside.
Depending on the design and placement, you might wish to open the vents as a “peep-hole” before you attempt to open the door. However be aware that the vents may be HOT, and you would need to protect your hands and keep your face clear of them in case of flame. External fire that has consumed most of its oxygen will quickly find a new source via the peep hole – it could turn your peep hole into a flame thrower, so stand to the side and check before placing you face to the peep hole.
FAN FORCED VENTILATION UNITS
One way of keeping the place dry is to have van ventilation. This can be done with 240 volt power or 12 volt power. As this document focuses on the basic bunker, it will only address the 12 volt options.
I first envisaged a combined unit comprising solar power to charge a gell-cell battery which would both run the fan. provide decent lighting for a dual use purpose, emergency lighting and be a charging unit for your mobile phone.
It soon became apparent this would require regulator circuits to avoid overcharging, low voltage cut-off functionality and over-ride facility so you would not get stranded etc etc. All this meant cost, complexity and, worst of all, the bringing down of the whole unit if just one component failed.
This then dictated the fan unit be isolated from anything else, which actually allowed the battery to be taken out of the equation, leaving two simple components: - a solar panel and a 12 volt computer fan.
The beauty of this arrangement is its simplicity. Each day, the fan re-starts and gives a continuous stream of fresh air. These fans are designed to run continuously for years and are relatively cheap, or free if you simply take them out of discarded computers.
Mount it on a rack or in a box and place it on a shelf which is immediately below your bunker vent hole.
To have the fan blow instead of suck, simply reverse fan in unit, OR, simply reverse the unit and put the blowing face of the unit against the vent hole.
If you are into basic electronics (or know someone who is), you can easily measure the current draw of one of these fans, and simply get a solar cell to power it. Have the solar cell powerful enough to drive the fan even if it is in shade, so as to maximise your fan run time in the winter when the sun is lower. The ratings on solar cells are for when they are in sun or bright overcast skies.
If you links to suggested solar cell/s, it can be put into this article and shared with interested readers.
I measured the current of this computer fan at 0.12 amps (ie 120 milliamps) on 13 volts, that’s about 1.5 watts. It is important your solar cell can turn the fan even if it is in shade, as it is likely to be for much of the day if there are trees about.
[pic]
It even ran as low as 5 volts, drawing 0.04 amps (ie 40 milliamps), that’s 5 x 0.04 = 0.2 watts. At that speed it pushed about a cubic foot every 10 seconds, that’s about 6 minutes per cubic metre. At 11 volts / 0.1 amps / 1.1 watts the airflow was about tripled.
Have the higher vent sending the air OUT and the lower vent having the air come IN.
You can get an idea if how well it clears the air by having a smoker briefly light up a cigarette in your bunker, then have him/her leave, then see how long it takes for the fan to clear the bunker of the smell of cigarette smoke.
IMPORTANT – vent must NOT open directly to where it might be directly exposed to radiant heat. This means it should only go to the roofed outside corridor OR down a metal pipe which can be covered over by a paving stone and/or soil.
The other exit / entry point for air is the resealable drain hole or a second sealable vent.
See also diagrams at the end of this document.
SPECIAL REQUIREMENTS FOR PETS
Pets will need to be stopped from escaping; and be able to be separated from people. Pets may be unpredictable and may bite or scratch viciously in such stressful circumstances. Also, you do not want them under your feet causing trips and falls. Because of this, cages are preferred.
You will also need food and water for them along with food and water dishes, and a can-opener if required.
Allow room for all this in your bunker design, and also possibly tethering points and (short) leads.
A rug that you can dampen to put over their cage if required will help protect them from smoke and super-heated air.
See also previous note regarding the need to keep them locked up or tethered for a considerable period after the fire has gone because of the significant danger of them burning their paws on hot ground or hot coals. So make sure you really do have plenty of water and food, as it may be a while before you can replenish stocks.
DESIGN FOR LATER EXPANSION?
Trying to build in opportunities for later expansion has problems – mainly of maintaining structural integrity – and why would you not want to build it to best standards from the outset? For reasons stated earlier, if you intend a dual use, a purpose built separate structure may be more cost-effective for that second use, which may built now or at some later time.
LOCATION – WHERE SHOULD YOUR BUNKER BE BUILT?
Having considered all of the above, now you can figure out where to put it.
See also diagrams at the end of this document
Considerations include:
• Not be near:
o your house – which, if it catches fire may burn for a long period and make entry/exit to your fire bunker dangerous;
o trees – which when burning may give off huge amounts of radiant heat, and might possibly fall onto the bunker or block the entrance;
o garages – which often hold flammable materials;
o your neighbour’s property boundary – because you have no control over what they put there.
• Not require you to go past hazardous areas to get to it.
• Drainage and flooding considerations.
• Pipe and cable locations.
• Future use of the area – eg if later you intend to add a workshop, pool or some other structure or feature on your property, don’t place your fire bunker in the way if it.
• Having the fire bunker easily accessible.
• Making use of any slope of your land – to enable partial or complete covering of it by soil, and preferably where a fire will simply go over it. Remember also that fires go much faster UP hills than down hills.
• Aesthetics – you probably live where you live because of its beauty. With some effort, you can maintain that.
The highest probability of bad fires is on days of northerly winds, so you would easily conclude it was better to have your bunker to the south of your residence, so it would be less likely you’ll have to go towards the flames to get to your bunker.
However Dr Kevin Tolhurst, giving evidence to the Royal Commission, said that 80% of the damage is done when the south-west change comes through. This is partly because by then the fire front is wide.
So possibly slope it the most important factor to consider – because a fire will go more quickly UP a slope than down it. But of course you need to be able to go UP that slope quickly.
This might be one of those issues where luck plays a part – so you should take into account all other factors first. Install it close enough to get to in a few seconds, but not so close that it could be heavily affected by a burning house.
See also diagrams at the end of this document
CONSTRUCTION MATERIALS AND METHODS
Early fire bunkers, or “dugouts”, were made of logs, with a roof of more logs or tin, and covered with soil. The soil gave the required insulation and fire-proofing. The entry tunnel was usually curved to give protection from radiant heat, and the “door” was well inside and consisted of blankets or hessian bags strung up and, in the event of fire, being wetted down.
With the foresters’ heavy cutting and earthmoving equipment, they were quick and cheap to build. However their inability to be sealed meant there was a risk of smoke and of oxygen deprivation.
Modern methods of construction include:
• Brick or Besser / Boral Block (Fire proof bricks and blocks are readily available).
• Some double bricking to ensure the protection of the inner layer and maximisation of the aesthetics of the outer layer.
• Pre-cast concrete tanks – modified – but be aware of our need to protect the doorway and door from direct heat. (See Links section for commercial suppliers.)
• Adapting pre-cast pipes or box culverts.
• Pre-cast concrete panels. (see )
It is imperative that your chosen material
• is not affected by direct heat, or is protected from direct heat; and
• remains sealed in extreme conditions.
Reports from Black Saturday noted that even cast concrete was not immune from the effects of heat if it was not protected from the flames and the extreme radiant heat.
Roofing may be concrete. This may be built by:
• a slab of concrete poured straight onto Clip Lock roof panel, but requiring some support during the pouring until fully set.
• making up wooden formwork and then the concrete poured onto reinforcement.
NOTE – roof concrete will require reinforcement, which is really easy to purchase and to include in the concrete pour, to protect it from collapse caused by vehicles, falling trees, degradation or simply the weight of the soil on top of it.
Some bunker suppliers advise their bunkers’ roofs are strong enough to hold a fire truck.
Bearing in mind that past or new trees may affect the foundations, the structure MUST be built on a strong reinforced slab that won’t distort and potentially upset the sealing of the walls and roof.
The importance of the structure being sound cannot be overemphasised. The last thing you would want is for it to become an oven, to allow smoke to get in or the oxygen to be depleted, or for the thing to collapse at your time of need. Do not underestimate the pressure that can be excreted by the surrounding soil, particularly when it gets wet. Block buildings will require very sound engineering techniques and reinforcing to maintain their strength.
ABOVE GROUND, IN-GROUND, TOP DOOR OR SIDE DOOR/S?
ABOVE GROUND:
|Advantages |Disadvantages |
|may be easier to build on flat ground |exposed, no natural protection from radiant heat or flames |
|no land-slip or drainage issues |no cooling from earth – will heat up in hot weather |
|easy access from side door |aesthetics – might always look like a bunker … or a public toilet |
|no excavation required |not optimal for dual use as wine cellar |
|easy drainage | |
|Special design requirements |
|double bricking to provide additional insulation |
|may require extra work for roof to be insulated (eg scoria rock and /or soil on top, layer of hollow blocks on side etc. |
|work on aesthetics (special blocks, creepers, features/sculptures/plant holders on wall) |
INTO SIDE OF SLOPE:
|Advantages |Disadvantages |
|soil provides insulation and keeps structure cool |requires excavation |
|minimal exposure to radiant heat |possible drainage issues |
|flames can go over it |some engineering possibly required |
|hidden from view | |
|still has easy entry | |
|Special design requirements |
|drainage |
|possibly waterproofing |
|embankments, wall and slab to be appropriately engineered to withstand weight of soil, particularly when it’s wet |
|method required to ensure bunker does not “float up” if soil is waterlogged. |
IN GROUND:
|Advantages |Disadvantages |
|no walls exposed |requires excavation |
|stays cool |potential for flooding into bunker – difficult to pump out |
|aesthetics – does not clutter up your block |ventilation challenges |
|not expensive if simply a small tank dropped into hole |if it is a small tank, it may be claustrophobic |
| |if in heavily treed area, ongoing fire may heat roof |
| |danger of children falling in. |
|Special design requirements |
|may require tank to be installed in very slight angle, so any water will pool at one edge, making removal easier |
|must be appropriately engineered to withstand weight of soil, particularly when it’s wet |
|if in heavily treed area, may require some soil and/or scoria on roof |
|method required to ensure bunker does not “float up” if soil is waterlogged. |
|Special maintenance requirements |
|regular checking for water and removal of any |
|regular venting |
TOP DOOR (FOR IN-GROUND)
|Advantages |Disadvantages |
|simple arrangement |not a simple method of access |
|no extra walls required |does not lend itself for convenient dual usage of bunker |
| |venting problems |
| |small children may fall in |
| |may bring on claustrophobia |
| |outward swinging door may be stopped form opening by something falling on it |
|Special design requirements |
|steel “roll-cage” type frame around doorway to protect if from any falling tree or debris and keep vehicles off it. (See also Signs section of this |
|paper and diagrams at the end.) |
|Alternatively, concrete or block “risers” to protect the entry |
|special attention to location and drainage to ensure no water-flow or soil erosion into door |
|facilities for pumping out any accumulating water |
|ventilation arrangements |
SIDE DOOR: (FOR IN GROUND)
|Advantages |Disadvantages |
|easier access than top |if you need to down into entry pit, potential for flooding in pit, or even the |
|easier to pump water out of unit |bunker |
|more opportunities to build in vents |potential for water damage to doors |
|Special design requirements | |
|drainage |Consideration of SIZE of door for ease of access and if dual use contemplated. |
|facilities for pumping out any water | |
HOW FIRE-PROOF DO I HAVE TO MAKE IT?
That’s not an easy question to answer. The more combustible material about, the hotter the area will become and the longer the main fire, and the remaining fire, will hang around. Other factors will be the direction that the fire approaches, how sheltered your bunker is from the fire and how much radiant heat it will be exposed to.
There are a range of things you can do, with each one making the structure more likely to achieve its objectives of keeping you and your family safe, and possibly even comfortable.
• An exposed metal bunker will heat up extremely quickly (so that’s clearly out).
• An exposed bunker made of a single thickness wall with hollow blocks will heat slower.
• Surround your bunker with soil and it will slow down the heating process, and also protect the blocks from potential structural breakage from the heat, and send the flame over you (but you will need to engineer the structure to cope with the pressures of the soil around, particularly when wet).
• Put in some scoria rock on the roof and against the walls before adding the soil and it will work even better.
• If you can’t have soil around it, a second hollow block wall around the inner hollow block wall (with a bit of space in between) will further insulate it and also protect the inner wall from potential structural damage from the heat.
• If the walls are made of fire rated blocks (these are readily available) then their ability to stand up to the heat is enhanced.
The new building codes were released Wednesday 11/3/2009. See:
Quoting from the media release for Friday 6 March 2008: ((2).doc
“The standard was due to be adopted by all States and Territories in May 2010. It will be effective in Victoria from Wednesday, 11 March.
The new Australian Standard will apply across the whole State, and areas will be defined under six Bushfire Attack Level (BAL) categories from low to extreme risk.
Every new home built in Victoria will undergo a BAL assessment as part of the application for a building permit. This will determine the method of construction to be used to better protect properties from the threat of bushfires. …….
“This year’s devastating bushfires have rewritten the rules, registering temperatures in excess of 1200 degrees Celsius and wind speeds of more than 120km/h,” Mr Brumby said.
“Prolonged drought and climate change require action on building standards, particularly in bushfire-prone areas. We must take into account extreme fire activity in building new homes.”
Based on 2008 building permit activity for new homes, 80 per cent will have the lowest rating – BAL-LOW – which will not require any additional measures.”
There is a description of how a BAL applies at: (6_March).pdf
In theory then, in a low BAL (Bushfire Attack Level) area, just as new homes built will not be required to be as fire-proof, your fire bunker need not be as fire-proof. Against that, houses burn down all over the place, not just in high BAL areas.
You may choose to do some calculations on the difference in cost of a BASIC fire bunker vs one with the HIGHEST PROBABILITY of survival, and consider whether you are prepared to risk your life, and those of your children, on the money you might save.
I suspect that after you allow for the cost of the base and roof, there is not going to be a huge difference in single vs double bricking, scoria etc,
Further, the cost of the second entrance (fire door, frame, seals and latch-set) will be made up with the extra peace of mind and extra habitability a cross breeze will provide, with the added advantage that your bunker will be dryer and not smelly. This is important for both you and your wine (!!)
Notwithstanding the above, you may decide that your going minimalist will do. You may be right, you may not. I hope you never need to find out, and if you do then I hope you are right.
WHAT ABOUT A BURIED STEEL CONTAINER?
With the appropriate preparation success can be achieved. A steel container would require plenty of insulation, for example fully bricked over or fully covered with soil, with no part of it potentially exposed to outside world. Protection against corrosion in the long term can also be a problem and must be addressed. Reinforcement may be required.
They have the same requirements for vents, sealing and drainage, and inward opening doors (if preferred/possible) which are protected from the flames by roofed corridor/s.
For story and pictures about this bunker, see
You will know little of the paint that has been used on them and it is not clear what sort of fumes they might give off if they were heated. However that should not be a problem if they are well protected from the heat. Some containers recently converted to housing in the mines were found to have been fumigated with formaldehyde, which caused health problems for their occupants.
THE USE OF SOIL AS A BARRIER
Using soil against the walls and roof is recognised as an excellent method of providing insulation from the heat. This protects the building materials and stops them from losing their integrity and effectiveness, and seals any cracks that might allow flames or smoke entering. The use of scoria rock against the walls and on the roof can increase the insulation.
(CSIRO paper on Lethal soil temperatures during burning of masticated forest residues:
Site to get paper: )
A sloped site may assist you to have the bunker integrated into the surroundings.
DRAINAGE
It is important that the site is well drained, for example with the use of slotted pipe around the base, leading the water away. If there is soil on the roof and against the walls, a waterproof barrier to stop ground-water and rainwater entering into the bunker may be required.
A well placed drain-hole in the floor will allow any water inside to drain away, and also allows the structure to be hosed out. However it can also compromise the ability of the structure to keep smoke out. An un-sealable drain hole in the floor has the same problems as unsealable vents.
A sealable drain-hole is possible, but avoid to avoid complexity that you would not want in an emergency, you MAY prefer to keep it closed, only opening it when you perform your regular maintenance, unless there is an ongoing problem of flooding or you are ALSO using it as a vent. Having it closed will also stop bugs crawling in when your bunker is not in use, but still also spray down some surface spray periodically.
If it is installed in the floor, you will need to install the outlet pipe, similar to the outlet in shower base, before laying the slab, have the shape/slopes of the slab direct all water to the drain hole and finally install the hardware for the resealable lid over the hole. If the outlet is simply installed in the bottom of a wall, similar concepts apply, however ensure your design does not allow the opening to be exposed to radiant heat.
The simplest plug may be a wet rag over the drain hole and a paving stone over the rag.
The outlet hole must be clear of walkways and swinging doors and gates so the plug does not get in the way of them or be tripped over, but still be easily accessible.
POTENTIAL FOR GROUND SLIPPAGE / COLLAPSE and EROSION
Altering the natural course of water can have an impact on the stability of the surrounding soil, with calamitous consequences if the slope is steep. Water which might previously have run under the slope might become be “dammed” underground and eventually the unstable dirt may give way, upsetting your bunker’s foundations, or those of other structures, or causing severe bank collapse or undermining the roots of large trees.
Water can also run between the soil and the sides of your bunker, constantly eroding the soil.
It is for these reasons that councils require engineering drawings for retaining walls and the like, with allowances for local water flows and drainage and sudden storms.
MOULD AND MICROBES
These are less likely to occur if the structure is kept dry, which is easier if it has been well designed and well built and there are two entrances, with doors that can be left ajar when the fire-bunker is not in use, or (preferably) having sufficient venting. Clever design of the entrances can allow the directing of the prevailing breeze through into one of the entrances, with a drying cross-breeze going through the bunker.
SPIDERS AND BUGS
These can be deterred with surface spray, insect spray and periodic use of an appropriate product such as a Mortein Flea Bomb. Having aluminium flywire on the vent/s and drain (both ends) will also help keep them out.
SOIL TYPES
Different soil types may require variations on construction methods. Get advice on what you need to do to accommodate these.
Soil types include earth or clay, sand, rotten rock, rock, flooding land, shifting sand dune and contaminated soil
POWER AND LIGHTING
Having 240 volt power connected it not recommended for your basic fire bunker. Remember that in a fire, there probably won’t be any 240 volt power available.
In non-fire times, having live cables around, particularly in an structure that may become damp, may be a recipe for electrocution. Any 240 volt electrical work MUST be done appropriately by a qualified electrician and must meet the demands of underground use. Robust and water-resistant outdoor type switches will need to be used.
One resident who protected himself in a bunker reported the flames shooting like a blowtorch into his haven through the conduit for the cables, melting their insulation. Cables will need to be safely “snaked” into the structure to minimise this possibility.
Lighting alternatives include:
• simple reliance on torches, possibly with the addition of;
• installing 12 volt power, possibly with a small external solar cell with a regulator to allow trickle charging and avoid deterioration of the battery through overcharging. However for the reasons above, ensure cabling is appropriately placed so flames cannot shoot in, and totally separate the running of the positive and negative wires to ensure any melting of external cables cannot cause a short circuit. Light can come from simple 12 volt LOW WATTAGE lights, garden lights or fluorescent lights. Ensure there is a fuse in the circuit and keep a store of spare fuses, or put a circuit breaker in instead.
Note that you must NOT have unsealed lead acid batteries in your bunker because as these charge they create hydrogen, which is a very explosive gas. Sealed jell-cells do not have this problem but your regulator will need to be calibrated for them.
If you are into gadgets and using a 12 volt battery, consider having a “cigarette style” lighter socket attached, and keep a car-charger for your mobile phone (around $20) in your bunker. However be aware that an unattended phone charger can flatten a battery.
A really simple and cheap alternative is have a line of garden solar lights leading to the bunker. These show you where the bunker is at night, or when the sky has been blacked. They can be easily pulled from the ground and taken into the bunker and can give you basic safety light for hours. When you know the fires are about, put a couple in there – and bring in some more later if you have the opportunity.
Most important are the working torches. Also consider a wind-up torch that doesn’t require any batteries. They have LED globes and often include a radio. Because they are not robust, I recommend you have both a wind-up torch AND a battery torch, not simply one of them.
The 12 volt system is probably overkill for a structure that you hope to never have to use in your lifetime, but if you are also using it for a wine cellar and you are not going to require the lights for long periods at a time, the 12 volt arrangement with appropriate lights should be fine, and possibly cheaper than arranging 240 volt cabling etc.
If you are building a super whiz-bang wine cellar, or some other dual use structure then by all means put in 240 volt power, but get it right and keep it safe,
FLOORING AND FLOOR COVERINGS
Floor covering can complicate things. Carpets and rugs can get damp or combustible, and vinyl slippery and can be combustible and the damp under it can cause smells, mould and other nasties.
If you must cover the concrete floor, make sure the covering is easily removable, and if it is not going well then get rid of it.
Make sure your concrete slab does not have a smooth finish as wet smooth concrete can be very slippery.
DÉCOR
For the sake of the children and for folk who may be susceptible to anxiety that can come with an approaching fire, a small amount of effort to make the room friendly may make it less fearful.
Simply painting the ceiling white may increase its ability to reflect light, and thus increase the brightness of the room in torchlight.
Do NOT line it with plasterboard or timber as these may camouflage any subsequent defect, such as a crack, that you need to be aware of and repair.
Use only water based paints.
BUNKERS AND CHILDREN
There are two schools of thought on bunkers and children
1. If you have kids, you may choose to paint appropriate murals on the walls (but use light colours) of hills, trees or whatever takes your fancy. Having the kids be part of this process makes them feel it is theirs and it will be recognised as a place of sanctuary, not a place of fear.
ALTERNATIVE VIEW
2. Because of the potential FOR CHILDREN TO BE LOCKED IN AND SUFFOCATE, children should be taught that it is a place of refuge, not a cubby-house, and you should not try to make it an attractive and tempting place to play.
Note however that you CANNOT guarantee your children, visitors’ children or uninvited children or trespassers will not enter, hence the need for:
• open vents – above where a small child can reach;
• doors that cannot be locked from either the inside or the outside;
• simple door latches; and
• not leaving dangerous items in the bunker.
With poor design, there may be a greater probability of tragedy in non fire times than there is in a fire. This is one of the quandaries presented to the authorities, and anyone considering the installation of a fire bunker.
BENCHES, SHELVES AND HOOKS
Shelves will allow you to put important things that you want to keep off the floor. Make sure you put them where they will not bump heads, particularly if folk make a hasty entrance.
Hooks will allow you to hang up torches and clothing and keep rags and essential tools from cluttering up the floor.
You may wish to install benches for seating and so children don’t have to sleep on the floor. At the end of this article there is a list of things you may wish to bring into the bunker, and these can be kept in plastic boxes and put under the benches, if the benches are designed appropriately.
For reasons of child safety, make sure the placement of your benches and vents do not allow a small child to stand on a bench and close over a vent.
COMMUNICATIONS
A radio can give you information about what is happening locally, with ABC local radio being the emergency broadcaster. However be aware that they may not have all the latest information on your immediate area.
Ensure your radio WORKS and have spare batteries on hand. Also consider the wind-up torch/radio referred to earlier, that doesn’t require any batteries.
It is recommended that you see if your radio works within the bunker. It might not, but that is not essential. If you have a portable scanner or similar, you may wish to bring that in too.
Your mobile phone may or may not work in the bunker. Try it out. Also be aware your mobile phone might not work during or immediately after a fire as the fire might disable the local communications infrastructure.
At least one bunker supplier is also selling safety beacons.
SIGNAGE
You might wish to have signs pointing to your bunker entrance, for the benefit of visitors etc. These can be fireproof so they also show the whereabouts of the bunker after the fire.
Have reflectors attached to it so it can be easily seen when lit up by torchlight or vehicle headlights.
To enable folk to find the bunker after the fire, you might want fire-proof signs, made of flat steel with letters cut out, stencil style, or weld cut-out or bent-rod letters to a frame securely mounted on steel posts.
Immediately after the fire, hang a bright cloth from it so that rescue services will easily see it as a “place of life”. BUT NOTE THAT THIS FRAME MAY BE EXTREMELY HOT IMMEDIATELY AFTER THE FIRE AND IT SHOULD NOT BE TOUCHED UNTIL COOL
You might with to keep your flag in your shelter, possibly with some reflectors and a flashing bike light. And take some of your solar lights out.
The Fire Refuges in Victoria: Policy and Practice: 10/2005 position paper : suggested this as a standard sign. No mention is made of reflective lettering or its ability to survive a fire (stencil style, raised lettering or steel lettering), but these could be worthwhile.
You may wish to design your sign holder as part of an integrated “roll cage” type arrangement to provide your entrance / door opening with additional protection from falling debris, and to hold any solar panel/s. See also diagrams at the end of this document.
MAKING YOUR FIRE BUNKER BLEND IN / LOOK GOOD.
There is a large choice of bricks / construction materials, and you may wish to have soil around and above it which not only provides insulation and protection, but can be covered with plants such as succulents.
If you wish to choose “designer” style bricks, these might not need to be fire-proof for the outer wall, even if you choose fire-rated bricks for the inner wall of your bunker.
Avoid plants which:
• may become a fire hazard near entrances;
• may cause structural damage because of their roots or if they fall; or
• require considerable amounts of water – which may leak or seep into your bunkers’ walls or roof, causing dampness, corrosion, flooding or mould.
OXYGEN / AIR SUPPLY TANKS & COMPRESSORS
Do NOT bring in an oxygen tank. Raw oxygen is EXTREMELY dangerous around fire.
In a reasonable sized space you could expect your available air to be sufficient until the initial fire front to have passed, however if your bunker has leaks in it, this time will be reduced.
Not long after, you would expect the available air outside to be again oxygenated for you to breath – even if this might not necessarily be pleasant because of the smoke.
I note that the standard bunker from Fireshelters and Fireproofshelters claim “There is sufficient air in a small Fireshelter [5 cubic metre] to sustain safe and comfortable breathing for 4 adults for over 2 1/2 hours.”
Methods of keeping the poisonous gasses out include:
• Best possible door and vent sealing arrangements
• Increasing the air pressure in your bunker slightly, by gradually releasing compressed air, so the smoke and gasses can’t get in.
However using the KEEP IT STRICTLY SIMPLE (KISS) approach could suggest there are also risks in having extra things to go wrong or fall over, and the SIMPLEST arrangements is often the best.
For some basic info on Scuba tanks, see which says ”An 80 cu.ft. cylinder at 3000 psi contains 80 cu. ft. of air, [1 cubic metre = 35.3146667 cubic feet, so 80 cu feet is a spot over 2 cu metres] which is about the size of a small telephone booth. The air in a telephone booth at 14.7 psi (or 1 ATM, which is ambient sea-level air pressure) weighs about 6.5lbs. The air is compressed 204.08 times smaller to fit into the scuba cylinder.
The air stored in the tank of a standard compressor will do the same thing, provided of course that it was filled in a safe environment, but your basic air compressor you bought from the hardware or auto shop only pressurises to about 100 psi. However, see warning from contributor Neville below.
A correspondent advised me ”I have also been told that hospitals use bottled air which may be suitable for use in a bunker”.
One fire bunker supplier site makes reference to a Chemical Oxygen Generator however upon reading , this may have safety issues in a confined space with fire about, particularly if there is no apparent ability to control the rate or length of its output; it gets hot when operating; and raw oxygen is dangerous around fire.
I’d like to thank Neville, a reader of this paper, for the following contribution.
1. In your section on SIZE you note that you don't know the volume of air required. I have found a figure of 9,700 litres/human/day at:
That site gives states … “First a reference volume of air is defined as the volume one average human needs for breathing during 24 hours. This volume of approximately 9,700 litres/human called here one human-day (hum-day) is derived using an inhaled volume of 0.5 litre per breath × 13.5 breaths/minute × 60 minutes/hour × 24 hours/day (Lough, 1983)”.
However that site does not appear to account for the fact that when we are anxious we consume more oxygen, and, against that, we only use a portion of the oxygen we breathe in, so we can actually re-use stale air and stay healthy for some time. Eventually, the oxygen levels will drop and start to cause problems. See for a table on how different levels of oxygen depletion affects you, it with other gasses also around, this can change the equations.
Hand held oxygen monitors are available, but at this stage I don’t have the cost.
Neville also advises: -
2. After your discussion on scuba tanks (a good idea, yielding about 2 cubic metres of air), you say: "The air stored in the tank of a standard compressor will do the same thing". You can calculate the air that an air compressor will deliver using Boyle' Law (remember P1 x V1 = P2 x V2?). I have a (relatively small) GMC compressor in the workshop. It holds 24 litres at 800 kPa (i.e. 115 psi). if you let all that out to atmosphere (i.e. 101.3 kPa), then you can calculate the new volume V2 = (24 x 800)/ 101 = 190 litres. That is only about 0.2 cubic metres, useful for one person for only 28 minutes if you believe the numbers above. Given that there have been warnings that air from normal air compressors may not be healthy to breathe, I think it may be unwise to recommend the use of air compressors. (The danger apparently relates to the fact that normal air compressors use synthetic oils so that they won't oxidise under pressure, but they can be toxic).
Numerous sources on the internet suggest it is not just the available oxygen being a potential problem, but also the intake of poisonous gasses from the fire. This is where we need organisations such as th CSIRO contributing – to find out just what is and isn’t dangerous and just how dangerous. Is the advantage of the pressure keeping the smoke out greater than the danger of the effects of the oil fumes?
Neville has also contributed some valuable suggestions on the importance of strength in block buildings underground and in concrete roofs being reinforced, and I have taken them on board and revised these areas.
COUNCIL PERMITS – AND THE RAMIFICATIONS OF IGNORING THEM
The laws generally require that you obtain council permits for building structures such as fire bunkers. Buildings are required to be built to certain standards, to minimise the risk to occupants. These standards can include appropriate materials, drainage, structural integrity and door and ceiling heights etc.
It is possible your local council does not have approved standards for bunkers. (See next section.)
If you choose to ignore the permit process there are several risks to you.
• You may be fined.
• You may be required to dismantle the structure.
• You may be at risk of being sued by anyone who is injured, and have your insurance company not provide coverage to you for this.
If you are not happy with what your council does, you may choose to take action to have these rules changed. Be aware that this may take time, and councils generally go down a path which protects themselves from legal action (and their ratepayers from having to foot the costs of claims) and thus are conservative in what they allow.
It is possible there may be some change after the Royal Commission however this may take time and may require further research by organisations such as the CSIRO and evaluation of the results before agreed standards and regulations are determined.
Against all this, I am not aware of the requirements of building very solid WINE CELLARS, which you may choose to construct in a manner which has your precious bottles protected from all that nature might throw at them, and which by coincidence might happen to become your place of last resort should you unfortunately need it. (One wag retreated to his cellar and, noting they had a couple of hours to kill, shared the polishing off of two bottles.)
Any council folk / planners who wish to confirm or correct the above, please feel free to email me.
ONE DIY FIRE BUNKER BUILDER’S EXPERIENCE WITH COUNCIL
The following is one person’s experience, Yours may be different. Things may change over the coming months, or if and when new standards are released.
“I checked with my Council today to see if I should have got a Planning or a Building permit. Basically a Planning permit was not required because the planning scheme did not specify that a Fire Bunker needed a permit.
The Council Building surveyor said that as there were no standards or regulations covering a fire bunker and that the technical and safety requirements where not clear, there were no regulations that they could issue a permit against. Therefore a permit was not required. I suspect this will change post the Royal Comm. but it should not be retrospective.
An interesting anecdote, when I looked on the internet post Black Sat there was only 1 Aust site I could find that sold fire bunkers but now every concrete tank manufacture has a fire bunker in their range!”
LIABILITY AND INSURANCE ISSUES
If someone is injured on your property they can potentially sue you for damages. They can be successful if you are found to have been fully or even partially negligent.
Your householders’ insurance policy will normally pay for all liability claim amounts and solicitors costs.
Your installing or allowing to be installed a sub-standard structure will assist the claimants case. HOWEVER, if you have acted illegally, by ignoring building standards and/or council regulations, your insurance cover may become void and so you could be obliged to pay for legal costs and the amount of the claim award out of your own pocket.
BUILDERS
Builders are also required to comply with building standards and council requirements or they can put their building licences at risk.
They can be sued for faulty workmanship or be joined as a defendant in any legal claim by an injured person against you.
They also have similar insurance issues and their insurance company may refuse to pay if they have not complied with the laws/regulations.
Because of all this, they may not wish to build you a fire bunker unless it complies with all standards and regulations and the relevant permits have been issued.
Any builders out there who wish to confirm or correct the above, please feel free to email me.
WARRANTIES
Although builders warranties are outside the scope of this article, you may wish to make enquiries regarding these.
THE IMPORTANCE OF ADEQUATE INSURANCE ON YOUR HOUSE & OTHER ASSETS
Having adequate insurance:
• allows you to go about your life with less anxiety – because in the event of a loss the asset can be replaced;
• stops you from being tempted to put yourself into danger because of the potential for financial loss;
• allows you to rebuild if your assets are damaged or destroyed.
COSTS and TIME
Rough guess, $4,000 to $15,000 plus. Firmly establish ALL your costs BEFORE you start.
If doing it yourself, my rules of thumb are:
• Estimate the amount of time it will take and multiply it by five, or seven or more if you also have a social life. (!)
• Estimate the cost and multiply it by at least two. (!)
Any feedback on costs gratefully received.
MAINTENANCE
• Regular inspection -
o entrances being clear of accumulated leaves and rubbish
o control of surrounding plant growth
o clear access to entrances
o it not having become cluttered with junk being “stored” (!)
o structural defects;
o corrosion;
o dampness;
o bugs; (periodic surface-spraying / flea-bombing may be required)
o dead animals and birds
o doors and latches working (doors can expand with moisture and may need to be planed down a bit Make sure you have your jemmy bar with you when testing this!!);
o vent openability, closability and bird/insect-proofing (inside and outside);
o fan (if fitted) working and correctly positioned
o torches in working order
o radio in working order
o extra batteries for torches & radio/s
o all other mandatory gear all present and in working order.
One commercial supplier says they will do regular maintenance checks if required, for a fixed fee.
For some technical info on maintenance of fire doors etc, see
THINGS YOU MAY WISH TO PUT IN YOUR BUNKER TO BE FULLY PREPARED
If you know what you would like to put in, you can make sure you’ve built your bunker big enough.
Allow sufficient room so that things you bring in don’t clutter up the place and reduce its effectiveness as a safe fire bunker.
It is suggested that you put what you need in plastic boxes which are sturdy, can be stacked and also be used as seats or tables.
Some folk like to go minimalist, others like to be fully prepared. Adapt this list for your needs. HOWEVER, as stated previously, be aware that all the stuff you might like to take in may take up valuable air space, so make sure your bunker is big and roomy enough to accommodate you needs and still allow plenty of free cubic metres for you to move about freely.
(At this stage I am not aware how much air space is required per person for a (say) a 60 minute stay without additional ventilation.)
(See for a good succinct list)
• Jemmy bar – so it your door/s gets stuck you can get out
• Woollen Fire Blanket – (that you should normally carry in your car – see .)
• Water bottles – BIG AND PLENTY
• Torches
• Spare Batteries. Consider also wind up torches.
• Wallet / handbag, including credit cards, health cards, licences and copy of a bank statement (for ID)
• Keys
• Address/Contacts book
• Candles, for possible lighting AFTER the fire has passed.
• Matches
• First Aid Kit Include eye baths, saline solution and Stingos or equivalent
• Current Medications / Pill / Asthma puffer [an ABSOLUTE MUST for asthma sufferers]/ diabetic medications
• Gladwrap for burns - after they have been cooled and washed with clean water for 10 minutes. (Glad wrap is a useful first aid dressing for burns as it prevents moisture loss, and keeps the area clean. It also makes it easy for the doctor to assess the burn.)
• Spectacles
• Contact-lens cleaning kit
• Prescriptions for medications and pill and spectacles/contact lenses.
• Basic provisions (you may be cut off for some time after the fire) that can be eaten without cooking (eg muesli bars)
• Communications / Mobile phone
• Transistor radio and spare batteries for radio
• FOLDED chairs / card table
• Games (pack of Uno for the kids), Storybooks and favourite toy.
• Pens, pencils and paper / exercise books – for writing lists & for kids to draw on.
• Small sharp knife
• Personal toiletries (including toothbrush, soap etc) but NOT aerosol cans
• Toilet paper
• Buckets and large icecream containers (several) for washing and cleaning and emergency toileting.
• Portable toilet seat
• A pile of tea-towels/cloth nappies – to be used as
o face rags,
o hand towels,
o wet scarves.
o door seals (place wet against bottom of door);
o keeping people and pets cool;
o extinguishing embers
• Sunscreen
• Insect repellent (non aerosol)
• Bar of soap
• Spare boots / Shoes
• Spare clothes / including some heavy/warm jackets (for afterwards) and underwear / socks
• Hats
• Gloves (leather or non flammable) for during and immediately after the fire
• Face Masks / Smoke Masks
• Goggles suitable for protection from embers and smoke.
• Spare glasses, eg. your old pair of prescription glasses and/or cheap reading glasses.
• Sunglasses
• Knife / fork / spoon
• Reflectors and a flashing bike light (see Signs)
• Your “we’re safe” flag for your signpost, or use one of your rags and some lipstick(!)
• Shovel
• Metal Rake
• Hessian bags and Mop/s for extinguishing small spot fires
• Fire fighting knapsack / spray pack
• Bowls / cups
• Laptop, Computer box / hard-disk drive / iPods
• Precious items / Pictures
You can even buy hand held oxygen depletion measurement devices if you wish.
Prepare in advance.
Don’t put your life at risk trying to rescue stuff to fill your bunker with.
Nothing is really that important.
THINGS YOU SHOULD LEAVE OUT OF YOUR BUNKER
• Gas bottles and gas canisters
• Aerosol cans
• Oxygen bottles
• Lead Acid Batteries
• Styrofoam, which can leach toxins
• Fuel, or anything containing fuel*
(*One local fire-bunker supplier suggests you take in a chainsaw, however my view would be that the dangers of leaking fuel fumes in a confined space in an environment which could get hot are far greater than difficulties of not having a chainsaw when you get out.)
If you have other gear (equipment etc) that you wish to protect but it is not safe to put in your bunker, make a separate storage place/bunker which does not have the same stringent requirements for comfort/health or total sealing.
THINGS YOU SHOULD NOT DO IN YOUR BUNKER
• Sleep in there or light a candle without the doors and vents well chocked OPEN.
• Cook.
• Use a gas lamp or any other fuel lamp.
• Have a lit mosquito coil burning.
• Close animals in (without you) without them having ventilation.
• Leave children in there unattended whilst you are outside fighting fires. (The scenario of them being in there alone and you never returning is too distressing to think about.)
PREPARATION FOR BUNKER USE – YOUR FIRE BUNKER PLAN
You have a bushfire plan – which you’ve worked out and should practice.
You also need to have and practice your fire bunker plan.
This should be written down and kept in your house and ALSO
in your bunker in a clear plastic bag with a pencil to write down your entry time.
WHAT TO DO BEFORE YOU HEAD INTO YOUR BUNKER
(eg when fires are anywhere near or might occur.)
1. If you are NOT planning to spend a lot of time in there (eg overnight bunking), then close the vents (inside and outside), but leave the door/s open.
2. Bring in your pets and tie them up or have them in cages, with water available. (They might not be happy or comfortable, but they will be safe and will not be at risk of running into danger, or tempt you or a member of your party to risk life and limb attempting to catch them.)
3. Have your mobile phone with you (it should have been charged) or put it in your bunker.
4. Get on with your other fire preparation tasks around the property, but don’t leave yourself cut off from your bunker.
WHAT TO DO AS YOU HEAD INTO YOUR BUNKER
1. Firstly, if you haven’t got from the house the things on your list then you’re too late. NOTHING is so important that you need to take risks getting back to your house to get it.
2. Keep our children close with you.
3. Close over the outside vents if you have not already done so.
4. If able, pull out a couple of the solar lights you had near the entrance and take them in with you. Also take in your “spot fire” fighting gear.
5. Take a last look to make sure there is no-one still out there.
6. Turn on torch/es.
7. Close the door/s.
8. Close the vents.
9. If anyone has been burned, IMMEDIATELY put PLENTY of COLD WATER on the burn to stop the burning process.
10. TAKE A NOTE OF THE TIME and write it down.
11. Take a note of the NOISE, as later reduction in noise may indicated the most dangerous time has passed.
12. If you have compressed air in your bunker, turn it on low for very slow release, to make the pressure in the bunker slightly higher than the pressure outside, and thus reduce the probability of smoke coming in.
13. Check on everyone’s health and be careful with injuries. Administer first aid as required and BE VERY CAREFUL TO KEEP WOUNDS CLEAN. After the clean water on burns, put Gladwrap on to keep the wound from infection and to retain the natural moisture of the skin. .
14. Settle everyone down and keep them supported and calm. Be aware that panic and hysteria can occur in stressful and unusual situations and in confined spaces.
15. Settle and reassure your pets.
16. Wet some rags and put them at the base of the doors to stop any smoke.
17. Wet other rags in case you need them.
18. Keep an eye out for any smoke coming in anywhere else as well. If it does, try to use the wet rags to stop it.
19. Stop, have some water and settle down.
20. Attempt to use your mobile phone to advise friends of your predicament, that you are currently safe and where you are. If necessary, leave voice mails and text messages, which should possibly be sent to various key contacts.
21. Wait at least 15-20 minutes after you went in before you (a) turn off your compressed air, (b) listen for outside noise, compared with what you heard when you went in, and, if you feel it is appropriate, (c) attempt to have a look outside.
22. Be VERY careful opening your door or vent peephole SLOWLY and keep your face covered and well free of the opening, in case of flame entry.
23. If it looks safe to venture out, do so carefully, with good shoes and your safety gear on.
24. If safe, leave the door/s open for ventilation.
25. Attend to any fire fighting required on your property. Pay particular attention to your party’s safety and, if building are not burned, watch for late spot fires setting them alight, including through broken windows and in ceiling spaces. (MANY buildings catch fire well AFTER the main fire front has passed.) Check your neighbours too.
26. Try to ring / text your contacts and give them an update of your situation.
27. Mark your fire-bunker sign with a bright flag to show it is a “place of life”. Note this frame may be extremely hot immediately after the fire and it should not be touched until cool
28. Do NOT bring children out until it is SAFE and they are aware that things could be different. Reassure them of the importance of their own safety so that their exit is not traumatic.
29. Do NOT release your pets until it is absolutely save to do so. Many pets have been released too early and have burned their paws on hot ground and coals.
Note that one of the biggest dangers after the fire is from burnt limbs falling from trees.
Keep yourself and your family clear of danger,
drink lots of water and keep yourself fed.
AFTER THE FIRE HAS PASSED
• Register with the authorities so they know you are safe.
• Tell your family and friends.
• Re-establish your post box and telephone accessibility.
• Re-establish your online (email) presence.
• Arrange mail re-direction if appropriate.
CLOTHING
AAARRRRRGH!!!
TIME AFTER TIME AFTER TIME we see folk on the TV hosing their houses in the face of the advancing flames – or clutching their kids and dragging them to the car – and what are they wearing? Shorts, thongs, sandals, light short sleeve shirts, no hats and no sunglasses. NOOOOO!!
The fire authorities strongly recommend you have the following items of clothing in a cupboard or suitable place in the house for you and your family to have immediate access to, and that everyone knows where it is. See CFA and Fireready websites for more information.
• Cotton LONG SLEEVE shirt.
• Cotton jeans or overalls
• Cotton scarf – a tea-towel will do, to be able to be wet and put over your mouth to protect your mouth, throat and lungs from super-heated air.
• Woollen socks
• Leather boots.
• Wide brimmed hat.
• Sunglasses
• Smoke-proof goggles
• Gloves, such as cotton or leather gardening gloves
See for an excellent list.
IF YOU THINK THE RULES NEED TO BE CHANGED, OR MORE RESEARCH IS REQUIRED– DO SOMETHING ABOUT IT
Since I started to write this, authorities have commenced the process for the evaluation of bunkers, with tight timeframes. It is hoped this will bear fruit and not get bogged down or forgotten.
If you feel your voice may contribute to these issues not being forgotten, contact your local councillor/s, state and federal parliamentarians, community groups and media.
You may feel organisations such as the CSIRO should be funded to fully explore the best way to make safe havens for times that it is not possible to be somewhere else.
Be aware however that people in authority may wish to await the outcomes of the 2009 Royal Commission before taking further action.
You can see a full copy of the Report of the Royal Commission 1939 bushfires at:
The information relating to dugouts starts on page 34 of the document (which is page 33 of the PDF).
An extract is as follows:
"The design of the dug-out, despite the test to which dug-outs were subjected by the fires of January, 1939, is a matter for the most careful consideration, of which only technicians are capable. It is true that the efficacy of dug-outs in fires such as those of January, 1939, appears to have been proved. Nevertheless, it must be remembered that hasty generalization is dangerous. It is recommended that the matter be submitted to experts, of which there are many in the Public Service; and that such experts determine the best manner of construction.
It is suggested that in the event of this recommendation being acted upon, the experts should particularly consider the questions of ventilation, air-purification, location, design (for example: whether tunnel, or tunnel with cross chamber, or in flat country, shaft and drive), baffles for both air and smoke, storage of water inside dugouts, supply of medicaments (for example: the prevention or relief of temporary blindness and inflammation of the eyes), water sprays, and restoratives; the direction in which the entrance to the dug-out should face; the question of exposed timbers and sheet iron; and the various other suggestions which appear in the transcript of evidence. It is suggested that it is essential that technicians who may be considering the matter, should read such parts of the transcript as relate to the matter of dug-outs generally.”
A number of the recommendations of the 1939 Royal Commission have resulted in significant improvements in the area of bushfire fighting and bushfire safety. Those fires were now 70 years ago. Unfortunately, the work relating to fire bunkers appears to have lagged behind the evolution of modern building materials.
BUNKER BUILDING STORIES
Thanks to Diederik for sending me his story – at
LINKS
I have found the following, but little specifically covering fire bunkers, or having it all grouped together. (That’s why I wrote this document!).
For an overview of the Black Saturday bushfires, see
Fire Refuges in Victoria: Policy and Practice: 10/2005 position paper from Victoria’s Office of the Emergency Services Commissioner
“This document expresses the Victorian Government’s policy position on designated public fire refuges and sets out a range of associated information about refuges, including responsibilities and a process for decision making, fixed and operational performance criteria for refuges and discussions on management and risk minimisation for the providers of refuges.” [Note from IP - experiences of Black Saturday make some of the info seem obsolete. There could be some great conversations about some aspects in light of recent lessons!]
Document:
Web page: (PDF)
CSIRO Victorian Bushfires Q & A (includes reference to fire bunkers). See also numerous other CSIRO pages (but unfortunately nothing on fire bunkers).
The Bushfire Cooperative Research Centre (Bushfire CRC) has produced numerous Research papers and reports related to Bushfire Building & Construction.
CFA website
CFA survival guide
CFA’s Living In The Bush workbook
Fireready website
Boral Blocks brochure / specifications
Pyropanel fireproof doors, doorsets and seals
Selleys Fireproof Cement
Black Friday stories
Black Friday Aftermath – includes info on dugouts
More stories from that site - . Click on the names on the right of that screen to see more stories.
Report of the Royal Commission 1939 bushfires
Alliance for Fire and Smoke Containment (PFPA). LOTS of technical info from the manufacturers.
New building codes were released Wednesday 11/3/2009. For info see:
Media release for issue of new building codes ((2).doc
New building code info – “Guide to building in Victoria after bushfires”
(6_March).pdf
Pre-cast concrete panels – brochure from the American Precast/Prestressed Concrete Institute.
Various other sites, mostly from USA and relating to storm shelters etc.
NEWS ARTICLES
BUSHFIRE TALK Evolving and informative newsy site for people in bushfire-prone areas
COMMERCIAL BUNKERS AVAILABLE FOR SALE
(but see notes in this article regarding insulation of bunker and protection of its walls and entrance from radiant heat.)
Alternate Dwellings
[pic]
FireShelters / Fire Proof Shelters
(Seems to be the same product as )
Their safety page is particularly good reading: and they’ve got a
youtube advert
[pic]
Fire Bunkers Pty Ltd is currently collecting information, and possibly awaiting further development of building standards, before developing a bunker possibly made of slab concrete. You can register your interest at .au. (I’ve registered and apparently they will email me some info, but at today’s date I have not received it.) No pictures on site.
I have no connection whatsoever with that organisation – I discover their site after commencing this article, and found they were saying the same things as I was.
• The Firebunker is not designed to offer residents an additional incentive to remain under the threat of fire, but to offer a vital alternative if residents find themselves unable to leave.
• We envisage that fire bunkers will be able to offer this desperately needed product in building safety by July 2009.
Statewide Fire Bunkers No pictures on site, but say their bunkers are 4.1 x 2.4 x 2.4.
Versatile Tanks
Available in 22 500 Litre - Size: 2.4m wide x 2.6m high x 4.4 long, mould manufactured.
Fire Safe Bunkers – have also advised that they anticipate supplying from April 2009, after release of the 3/09 building regulations. Cost for 15mm thick - 2m wide 2m high is $9,700 plus GST. Includes extras. They also advise bunkers are a “last resort when you have run out of options”
Timbercrete – Above ground Concrete Block unit sold in kit form. Includes pressurised tank so keep smoke from entering, fire resistant window and fire resistant spy hole.
[Note this is single thickness concrete block. Quoted test results show product’s ability of hold structural integrity in heat and an unacceptably high inside temperature (75 degrees) after 4 hours of that heat, but no info on inside temp after (say) 30 minutes of fire that can melt mag wheels. See also notes in this article about possible advantages of double bricking, and radiant heat through Windows.]
and
Bushfire Bunkers – based in NSW. Units come in two sizes, each 2.5 metres in diameter. The small model has an internal height of 1.485 metres, and the large model has 2.27 metres of head room. Side or top opening.
Firepit Australia Go to then click on Firepit Australia on the TOP of the page.
[My concerns about this unit include (a) how easy is it to get into and seal in a hurry and (b) it is stated the top door is rated to 1300 degrees C, which means the door will apparently retain its structural integrity, but there appears to be nothing about its insulation qualities, which are required to stop the trapdoor heating and radiating heat straight down to you.]
Bush Fire Bunkers Built of blocks, to your specifications, prices from about $5,000.
Victorian Fire Bunkers New to the scene, you can register your interest.
Aussie Bunkers Also appears to be new to the scene, you can register your interest.
, , and all direct you to which claims to be an information matching service to express interest in receiving information about fire and emergency safety bunkers etc, but their registration page was not working when I tried.
Cellar Creations – Pre-fabricated wine cellar pit. [Although not advertised a s a fire bunker, they come up whenever you do an internet search for fire bunkers!]
Earthlink homes Commercial and house builder, also do fire bunkers.
Waterford Constructions Safety bunkers - Fire fighting base stations, Personal family fire bunkers. [Looks like a concept rather than something which has yet been tested.]
[pic]
MineARK FireARK Chambers. These folk make STEEL safety chambers for the mining industry and are apparently thinking of turning their hand to fire bunkers.
[The exposed steel walls are a worry if not buried] “At this stage, MineARC has made itself available for consultation with local government and the related authorities and is currently assessing existing fire and safety standards and regulations.”
Brochure at:
Economy tanks - A correspondent advised me that “I also spoke to Economy tanks who produce a concrete tank that may be suitable (triple skin concrete construction)”
National Fire Bunkers - Complete Insulation and Service of Underground Fire Bunkers.
Flat Pack Fire Bunker - Pre-cast floor, walls and roof, 2 sizes, Looks interesting.
[pic]
Wildfire Protection Services is designing a small metal bunker with internal insulation.
Bushbunker solid purpose built unit with accessories built in.
and
OTHER PRODUCTS & USEFUL EQUIPMENT LINKS
Protect-A-Life Fire & Smoke Mask $60 (more products on that site)
More mask info
Relocation kit – list found on an ABC site – says much of what I have said in this article!
Smart Age Technology Pty Ltd says “We can provide a internal and external fire board to build houses and bunkers giving you 30 - 240 minute rating”
Wildfire Protection Services manufacture Radiant Heat & fire Shields to protect windows and doors etc. Also sells other gear.
Ceasefire sells various fire retardant paints and other products.
Woollen fire blankets used by the CFA and the Rural Fire Service in NSW. The Victorian one is thicker. You can buy the thick one (without the logo) from the manufacturer from . They also have a thinner version on the same page (less expensive, but I just bought the thick one for my sister.) Outlets in Creswick (VIC) or Hawthorn (VIC), see . Keep one in your car, pull it out if you need it at home.
See also
and
and
SAMPLE DESIGN, WITH 2 DOORS AND PROTECTED ENTRANCES
(You need to be in Print Layout view to see the graphics on this page. Go View, Print Layout)
This is NOT TO SCALE – as you will probably wish to make it longer to accommodate all your needs.
ROOFING - POSSIBLE CONSTRUCTION METHOD.
(You need to be in Print Layout view to see the graphics on this page. Go View, Print Layout)
Not that whilst this might be sufficient for normal usage, it may not be strong enough to hold a fire truck!
Get your own information about these things and remember the importance of signage.
ROOFING – CONSTRUCTION METHOD IF TWO WALLS
(You need to be in Print Layout view to see the graphics on this page. Go View, Print Layout)
DIAGRAM OF SAME STRUCTURE WITH LOCKABLE STORAGE AREA FOR WINE OR OTHER ITEMS.
(You need to be in Print Layout view to see the graphics on this page. Go View, Print Layout)
Structure to be surrounded and covered by soil.
Wall of inner area, which are not covered and are thus exposed to outside, to be double-bricked.
EXAMPLE OF MODIFIED CONCRETE TANK.
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Walls and roof MUST be WELL covered in soil as radiant heat can heat tanks to oven-temperatures.
Door needs to be fireproof and have sealing to stop smoke from coming in.
BEST POSITION ON THE SITE (also see next page)
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BEST POSITION ON THE SITE (continued).
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LOW VOLTAGE VENTILATION SYSTEM
SIGNS
THE HIDDEN IMPACTS OF BUSHFIRES
The following is extracted from an ABC story about the 1939 bushfires.
()
“It impacted on people who were burned out, it will happen again here as well. If you were just to go to Mount Macedon, the divorce rate just went boom, people who were just teetering on a marriage that wasn’t all that secure, just tipped them over the edge.”
It is important you recognise these hidden impacts of bushfires.
Be aware that
• your state of mind may not be someone else’s state of mind.
• your logic / priorities may not be someone else’s logic / priorities.
• the consequences of a ruined relationship may be more devastating than losing any physical assets.
• the anxieties and fears of potential bushfires can have similar effects.
Stop, listen, talk about it and allow others to say things to get them out of their system. Make it clear that you’ve heard them and be supportive, even if you don’t agree with them or even fully understand it all.
Stop, find someone who is supportive and who is a good listener, and let it all spill out.
You might never know why it works like this, it just does. And it might spill out at times when you least expected it, or in ways which could be hurtful to others or harmful to your relationship with others.
Take time to let the flurry of snowflakes fall to the ground and for things to get back to some sort of normality. You may need to be gentle and forgiving with others – and go easy on yourself too.
Just as the ash needs to be washed away to allow re-growth, all humans require the washing out of something inside them that they sometimes don’t even realise is there.
It just seems to be the way we are made. Learn to live with it, and learn lots from it.
Alternatively, ignore it at your peril.
The Age had an absolutely EXCELLENT article on getting over bushfires, printed 2 May 2009. Clinical psychologist and consultant to the Australian Red Cross Dr Rob Gordon, who has worked with survivors of 25 major disasters, has some excellent advice on rebuilding one’s life post the fires.
He refers to getting over being in “adrenalin mode”, and getting back to the things that are really important in your life. He says “Hang on to the big picture and think about what you can’t replace: your relationship, your family and children, your health, your career, your interests, your friendship networks. All this things that actually make life meaningful.”
You can read a full copy of the article at the end of this document.
EQUIPMENT AND OTHER HELPFUL STUFF
See CFA and Fireready websites for full details of equipment you should have around the time of a fire and how to protect our property in the lead up to the fire-season.
There are FOUR fire risks that your house is at risk from:
• Embers in advance of the main fire.
• Radiant heat from the main fire.
• Flames.
• Embers AFTER the main fire.
Small tools may include: metal rake; fire knapsack or sturdy back-pack sprayer; old style mop; plenty of water in open containers; buckets
If setting up INSIDE your house up for fending off the fires, as well as wet mops (ie the old style “rope” type mops), wet towels, and buckets, also have HOSES inside, attached to reliable water supplies. Remove your washing machine hose from the tap and screw a hose fitting onto the laundry tap and attach a garden hose.
If inside water is reliant on the continuation of electricity to your house, this is likely to fail during a fire. Mains pressure may also reduce with everyone using their hoses at the same time.
Outside (and inside), pumps can fail and hoses can be cut or burned. To be able to douse spot fires that might occur AFTER the main fire has passed, and your piped water supply / pump / hoses may be out of action, MANY pre-filled buckets will need to be available and can be easily filled from open containers, such as a swimming pool. Have your bath and basins full.
Have plenty of wet hessian bags. wet towels and wet mops available. You may get more mileage out of these for the water you have available.
Be aware that heat from the flames may not let you get anywhere near the flames.
Keep two woollen blankets and large unopened waterbottles permanently in your vehicle.
(For a scientific paper on vehicles in fires see . and for a source of woollen blankets see .)
THAT’S IT.
I wish you all the best in your endeavours, and look forward to hearing of how you went, the things you learned (good and bad), and perhaps get some pictures.
It might be possible for these to be put on a link from the opening web page (only with your permission and with or without your identifying details – as you choose).
Please don’t rely on me to provide your answers, all that I know is in this document (and the additional info is put onto updated editions of this document, as I learn of it).
There are individuals and groups out there desperately seeking the info, and unfortunately the organised accumulation of the relevant material in the community is still in its infancy. I have received emails from individuals, families, friends and relations in bushfire prone areas, builders, engineers and folk involved in local fire groups and land care groups. These groups could be a good place to go to meet like-minded folk working with the same issues.
The new building codes (released Wednesday 11 March 2009, were announced within a month of Black Saturday. However there is still much research apparently required into fire bunkers, made more difficult because the Black Saturday fires were something not been experienced before. The CSIRO has indicated these conditions are now more likely to occur again than in the past.
If you feel something needs to be done to ensure it does not all get bogged down, do something about it. Contact your local council and/or member of Parliament and make sure they are not sitting on their hands. As stated, some of these issues were first raised 70 years ago, but fell off the radar.
If I can write a document such as this, then imagine what you and your communities can achieve. Please do what you can to make it all happen.
Once again, do not RELY on this document, but I hope it helps you with your enquires.
All the very best. Ian Pullar ianpullar@
PS – Okay, if you’ve read right to the end – I may as well put in a plug for my other project, which is a budgeting book called Easy Budgeting – I’ll never be broke again.
Free download from
You never know – follow the hints and you might be able to afford your dream bunker (oops, I mean wine cellar).
SEE OVER PAGE FOR AGE ARTICLE
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AGE ARTICLE
When it comes to surviving bushfires – this is possibly the most important information in the whole document. A fire bunker may be able to save you and those who are important to you. The following is about keeping those people important to you – and keeping you important to them.
It says “Hang on to the big picture and think about what you can’t replace: your relationship, your family and children, your health, your career, your interests, your friendship networks. All the things that actually make life meaningful.”
We can fight long and hard for material things or “the way things should be” which may ultimately mean nothing if we loose the people around us in that struggle.
-----------------------
Unit in FIRE-READY position
Unit moved, Vent cover gets closed, or stuff hole with wet rag and put a brick with a wet towel around it hard against hole to seal it.
Also seal outside end of hole in wall.
Earth Fill around walls
OR double layer walls
Earth Fill
Secondary walls protect the inner walls from direct heat.
Inward opening Fire Doors,
with seals
If no earth fill, build a second wall outside, on slab.
Earth Fill around walls
Earth Fill around walls
If no earth fill, build a second wall around 3 sides. on slab.
Example of wall to catch breeze. Also further protects entrance. One on each opening may be preferred
There is no direct exposure to door from radiant head
Slotted drain pipe around base
Slotted drain pipe around base
You will probably wish to make it longer to accommodate all your needs
Closable vent in door
Closable vent in door
Bench with plastic storage boxes underneath
Shelf above bench.
Hooks
Hooks
Vents to be
bird-proof
Hollow Besser / Boral concrete blocks, fire rated if required.
MUST have roof over entrance
MUST have roof over entrance
THIS IS “FOOD FOR THOUGHT” ONLY. GET INFORMATION FROM PEOPLE WHO REALLY KNOW ABOUT THESE THINGS BEFORE MAKING PURCHASES OR COMMENCING CONSTRUCTION!!
WALLS MUST BE STRONG ENOUGH TO WITHSTAND THE PRESSURE OF THE SOIL, PARTICULARLY WHEN WET.
If you have two doors, it MIGHT be appropriate for ONE of them to open outwards, See document for more details.
Clip-lock steel sheeting
1. Lay a line of half-width bricks on top row. This is essential to seal the roof.
2. Cut and lay Clip-lock sheeting.
3. Lay concrete roof.
4. After concrete has set, waterproofing may be required before it is covered with earth to provide an insulating barrier.
Scoria rock can enhance insulation.
Block wall, hollow concrete blocks 190 mm wide. surrounded by soil or double bricked.
Fire rated concrete blocks and bricks are available.
Ribs to go across shortest span.
Must seal completely
Temporary support to be removed after concrete has set.
Concrete poured onto clip-lock sheeting. Reinforcement will also be required.
THIS IS “FOOD FOR THOUGHT” ONLY. GET INFORMATION FROM PEOPLE WHO REALLY KNOW ABOUT THESE THINGS BEFORE MAKING PURCHASES OR COMMENCING CONSTRUCTION!!
Slab may need to extend out for the building of outside walls
Strong reinforced concrete slab, with appropriate sloping and with any required allowance for drainage, doorways and the building of outside walls.
VIEW FROM SIDE
A convex roof will stop water pooling.
Minimum height, 2.2m
(I believe that’s 11 blocks).
Clip-lock steel sheeting
Concrete poured onto clip-lock sheeting. Reinforcement will also be required.
Clip-lock
Pad
Pad
Pads on the top of the to row of hollow bricks will seal the hollows in them, and the
second small brick barrier will stop the smoke from getting in through the folds/flutes.
Pads are available fro m your brick supplier
THIS IS “FOOD FOR THOUGHT” ONLY …
AND YET ANOTHER REASON TO GET INFORMATION FROM PEOPLE WHO REALLY KNOW ABOUT THESE THINGS BEFORE MAKING PURCHASES OR COMMENCING CONSTRUCTION!!
Clip-lock steel sheeting
Concrete poured onto clip-lock sheeting. Reinforcement will also be required.
THIS WILL NOT WORK for DOUBLE WALLED structures, as smoke can flow through the flutes / folds in the clip-lock sheeting if it breeches the outer wall
Storage area for wine or other safe items.
Lockable wire mesh gates.
Design of opening allows cross-flow ventilation for before and after fire
Design of opening allows cross-flow ventilation for before and after fire
Door
Door
Sealable vent in Door or in wall
Sealable vent in Door or in wall
MUST have roof over entrance/s
GET INFORMATION FROM PEOPLE WHO REALLY KNOW ABOUT THESE THINGS BEFORE MAKING PURCHASES OR COMMENCING CONSTRUCTION!!
If you have two doors, it MIGHT be appropriate for ONE of them to open outwards, See document for more details.
Reinforced
wall
holds
in soil
Sealable vent in Door or in wall
Sealable vent for cross-ventilation
MUST have roof over entrance/s
GET INFORMATION FROM PEOPLE WHO REALLY KNOW ABOUT THESE THINGS BEFORE MAKING PURCHASES OR COMMENCING CONSTRUCTION!!
NOTE – YOU CAN BUY CONCRETE TANK BUNKERS.
SEE LINKS SECTION IN THIS DOCUMENT FOR DETAILS.
Wall to protect door from radiant head
Slope
Slope
This bunker is better positioned as the fire is more likely to go over the entrance.
This bunker’s entrance is more likely to be exposed to the flames
ALSO remember that fires go much faster UP hills than down hills.
SIDE VIEW OF SLOPE
House
Also see
LOCATION – WHERE SHOULD YOUR BUNKER BE BUILT
in this document
Is it easy to get to?
What do you have to go past to get to it?
Not too close – or too far away from house?
Where are
• EXISTING and PLANNED structures
• Dangerous structures
• Roadways
• Pipes
• Cables
• Trees
• Future constructions
• Neighbour’s property?
What is natural flow of water when it rains?
Flooding or drainage concerns?
Are there any soil slippage or erosion concerns?
Where will entrance/s be?
It may be the steepness of your hill that dictates placement
Is the slope too steep to allow safe access UP to the bunker?
UP THE HILL
House
Is ACROSS the slope a better way to get to the bunker?
Is the slope too steep to allow safe access DOWN to the bunker?
DOWN THE HILL
Bird and bug barriers required on vents & drains.
If vent is a pipe, barriers are to be at both ends
Unit is in NORMAL position covering vent hole,
and drain hole is open
In FIRE-READY position Vent is sealed or BRICK (wrapped in wet towel) covers VENT & DRAIN HOLE is covered
Shelf
Entrance corridor
Unit
Vent hole in wall
Drain hole here
or
here
Ventilation unit blows out stale air and sucks in fresh air
Entrance corridor
Brick
Vent hole in wall
Drain hole exit also covered by brick
Ventilation unit is replaced by block, wrapped in wet towel, hard against vent hole, or clamp-down vent cover installed.
Drain is blocked with brick, wrapped in wet towel, hard against drain hole.
Brick
Brick
Brick
Solar Panel could attach to here
This sort of plate could also suit bolting to a brick wall, preferably with gap (use washers) between wall and plate.
Fire Bunker
(
(
Chain links welded to bar for your attachment of your “We’re Safe” flag
Solid steel bar heavily bolted to bunker roof, or sunk into ground with concrete footings
Steel sheet plate with letters pressed out stencil style, to survive fire.
Arrows can be bolted on in the direction to indicate location of bunker / door
Do NOT use aluminium plate.
Sign and arrows to be covered BOTH sides with reflective red tape, to show up in light from torches or vehicle headlights.
Reflective adhesive strip on bars
For top opening tank-bunkers, strong sign frames can also form a safety frame to protect door from vehicles and falling timber .
If you think this is a good idea and you work for / own an organisation that can build these commercially, why not offer your wares to the commercial fire bunker manufacturers?
If you do build them, tell me and I’ll add you as a link.
VIEW FROM SIDE
VIEW FROM SIDE
Unit in NORMAL position
covering vent hole
ROOF
FLOOR
FLOOR
ROOF
Which side of house?
Bird / bug barriers
Bird / bug barriers
Example of a Tank type bunker with a SIDE door.
They are also available with TOP doors.
Advantages and disadvantages of both are in this article.
TANK BURIED
INTO SOIL
[pic]
See also VENTILATION & FAN FORCED VENTILATION sections
[pic]
This is an illustration of a neoprene seal built into a door frame, from .
Presumably these are similar to the seals on your new oven door. However the Black Saturday fires were MUCH hotter in the open than an oven so it’s really important that your doors and frames are protected from continuous radiant heat by “corridors”.
Door IN frame
Walls &
Door surrounds
Walls &
Door surrounds
Door AGAINST frame
The Fire Refuges in Victoria: Policy and Practice: 10/2005 position paper : suggested this as a standard sign. No mention is made of reflective lettering or its ability to survive a fire (stencil style, raised lettering or steel lettering in an open frame), but these could be worthwhile.
The highest probability of bad fires is on days of northerly winds, so you would easily conclude it was better to have your bunker to the south of your residence, so it would be less likely you’ll have to go towards the flames to get to your bunker.
However Dr Kevin Tolhurst, giving evidence to the Royal Commission, said that 80% of the damage is done when the south-west change comes through. This is partly because by then the fire front is wide.
So possibly slope it the most important factor to consider – because a fire will go more quickly UP a slope than down it. But of course you need to be able to go UP that slope quickly.
This might be one of those issues where luck plays a part – so you should take into account all other factors first. Install it close enough to get to in a few seconds, but not so close that it could be heavily affected by a burning house.
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