American Tiny House Association



1 Existing copy and paste from as of Feb 6 2015

2

3 Purpose

The purpose of this program is to support the construction of safe and sturdy tiny houses on wheels (THOWs). Well established standards exist for recreational vehicles (RVs), residential homes on foundations, and manufactured homes (formerly known as mobile homes). Yet none is fully applicable to the THOW. In addition, construction of a THOW is often a Do-It-Yourself project, but professional associations are generally not accessible to DIYers.

THOW Certification is offered initially for the most popular type and size of THOW. There are many variations that are not covered in the Guidelines. This does not mean that such THOWs cannot be well constructed; rather that they are out of the scope of this program.

4 Alternative Certification via Inspection by PWA

An alternative to this self-certification program is available through Pacific West Associates. They offer inspection services for tiny houses, certifying that they meet ANSI 119.2 (NFPA 1192) or ANSI 119.5 (for park model RVs). Membership in the RVIA is not required. For more information, see their brochure or call Mario Huber at 307-315-0181.

|Notes: | | |

|This program doesn't cover tiny houses on foundations.Residential | | |

|building codes establish minimum standards for houses on foundations.| | |

|The codes, as well as various zoning regulations, include size | | |

|restrictions that make it challenging to build tiny. These issues | | |

|need to be addressed, but are not part of our program at this time. | | |

|Why is a THOW unique and not some other type of vehicle or house? See| | |

|below. | | |

5 Process

Tiny houses that meet the Guidelines stated below can be self-certified by the builder by completing a documentation package that includes the following:

Detailed structural plans illustrating the location of studs, joists, rafters, and engineered connectors (hurricane clips, tension ties, etc.). Plans must clearly address how the structure is secured to the trailer, and how the floors, walls, and roof are framed and sheathed. Plans must also include an illustration of a floor, wall and roof section, showing the building members, insulation, vapor barrier, moisture barrier, sheathing, siding and roofing. If unable to provide a detailed structural plan, then an engineer’s approval and/or a certification from a building inspector may work in lieu of this.

Detailed diagram of the electrical plan.

Photographs of the framing, roof, insulation, rough plumbing, and rough electrical.

Complete, detailed bill of materials. (Note: the DMV may require receipts along with a bill of materials at time of registration.) Where salvage or donated materials are used, the builder must provide a full description of the materials. It is recommended, but not required, that receipts be saved along with the bill of materials, as the DMV may request these when you register your THOW.

A statement signed by the builder certifying the house is built according to THOW Guidelines.

These documents will be uploaded to and stored at a central, website (not yet available for use). Builders will have control over who may see their documents.

Note: certification is a voluntary and free process by a tiny house builder who wants to record how his or her home was constructed. Certification is NOT yet recognized by any government authority and does not convey any particular benefits or special privileges. It is intended as a first step in establishing standards that might later be adopted by agencies when creating unique, new zoning or code regulations for tiny houses.

6 Guidelines

Definition: A tiny house on wheels (THOW), for the purposes of these Guidelines, is a structure which is intended as a full time residence or year-round rental property and meets these five conditions:

built built or moved onto (this will allow inclusion of shipping container homes and similar) and attached to on a trailer that is registered with the builder's local DMV.

towable by a bumper hitch, frame-towing hitch, or fifth-wheel connection. Cannot move (and was not designed to be moved) under its own power.

is no more than 8'6" wide, 30' long road legal in width and height, no more than 40’ long., and 13'6" high. Please note:

3.a. Some states are more restrictive. Here's a handy but unofficial summary of size limitations. Please check with your local DMV for the laws in your state.

Trailer GVW shall (or shall) be designed to account for owners possessions, and furniture that is not removed during transit.

3.b. Roof height is from bottom of tires to the top of the highest exterior point on the house, including any protrusions. The roof height may be taller when stationary, as long as it is collapsible for towing of the THOW, or overheight permits are obtained.

Chimney piping may need to be removed for travel and then reinstalled to meet clearance requirements for use. (overheight permits can be obtained for this, no need to include as a requirement.)

3.c. Slide-outs and tiltouts are permitted if the THOW plans have been reviewed, and approved/inspected by a structural engineer licensed in the state in which the THOW is built. (requiring it to be from a licensed engineer in the same state as which the home was built will exclude builders who purchased plans designed in another state, that may still be approved by an engineer. Any state licensed engineer will be qualified to review these plans.)

has at least 70 square feet of first floor interior living space, and no more than 400255 square feet (excludes any lofts).

includes basic functional areas that support normal daily routines (such as cooking, sleeping, and toiletry).

To be certified, a THOW (as defined above) must meet or exceed the following standards:

Note: The guidelines are intended to ensure safe and sturdy THOWs. Builders may use materials and methods that differ from those specified below, if it can be demonstrated that such materials and methods make the house safer and sturdier.

(A glossary needs to indicate that “builders” refers both to professional, and owner-builders, or it needs to be changed in each instance to professional builders and owner-builders)

Meet RVIA NFPA ANSI 1192 Standards (new link included) with the following exceptions:

1.a. The definition of Recreational Vehicle does not apply and is replaced with the definition of a Tiny House On Wheels (as stated above).

Wherever "RV" or "recreational vehicle" appear, the acronym "THOW" or phrase "tiny house on wheels" is to be substituted.

1.b. A secondary means of escape (egress window) is not required to be labeled, and there is no requirement as to the type or color of its handle.

1.c. Warning labels are not required. However, it is recommended that NFPA 1192 requirements for warning labels be met for any THOW that is intended for sale. or rental. and are required on any THOW intended for use as a short-term rental.

1.d. Similarly, an owner's manual is not required for THOWs inhabited by their owner; and thus any requirements that mention the contents in an owner's manual are not applicable. However, if the THOW is meant to be used a short term rental, documentation that covers safety and the THOWs systems is required.

1.e. Composting and incinerating toilets are acceptable, and when present, must be installed according to the manufacturer's specifications (which may be out of compliance with NFPA 1192 Chapter 7 which requires a toilet to be connected to a drainage system). Homemade composting toilets are allowed.

A free copy of NFPA 1192 is available at this link: click on “free access to the 2015 edition of NFPA 1192”

Be built for earthquake Zone 4 and able to withstand winds of 130 mph, as specified in the ASCE/SEI 7 Minimum Design Loads For Buildings and Other Structures.

Have adequate moisture barriers, vapor barriers, insulation, fans and vents to minimize condensation. These requirements go beyond what is specified in the IRC. and include… (this needs to be specific, link has broken url. If above code need to review this).

Be secured to a trailer that is adequate for the weight of the tiny house, its furnishings and occupants. The trailer must meet Department of Transportation (DOT) guidelines of the state in which the THOW is built. built registered and meet a minimum standard of (we need a specific standard for homes that may move state to state). The frame must be securely fastened to the trailer as specified below in the framing guidelines.

It is recommended, but not required, that the THOW weigh less than 10,000 pounds. Above this weight, some states have special driver's licensing regulations.

Use quality materials.

6.a. New structural components (steel, lumber, plywood/OSB, ties, and fasteners) should meet the International Building Code, Residential Code. However, salvage materials may be used if they are of equivalent strength and durability as new materials that are specified in the code. Materials not listed in the IBC will be allowed if approved by a licensed structural engineer. (this will allow shipping containers etc) .

6.b. Fasteners must be corrosion resistant at structural tie-points and where the house attaches to the trailer frame or foundation. This is done so that a future water leak, or the actions of chemicals in treated lumber, do not damage structurally important fasteners. The two most common types of corrosion-resistant fasteners are 1) hot-dip galvanized nails and screws, and 2) coated exterior screws. Stainless steel screws are recognised as a superior if more expensive fastener and are ideally suited for marine environments.

6.c. For engineered straps, hurricane clips, tension ties, joist hangers, and header hangers, use the fasteners recommended by the manufacturer. Only use the nails and screws designed for the engineered system. "Tico" nails are the most common. SD series screws can be used for anchoring straps and tie-downs.

6.d. For the interior "envelope" (enclosed space) of the house, materials (plastics, glues, insulation, paints, and finishes) must be approved or known to be chemically safe for interior use. (Strike, as not listed as who is to approve, and guidelines not specific)

Framing

7.a. Welded Steel frames: Steel frames must be secured to the trailer by welding to the trailer frame.

7.b. Wood frames: Wood frames must meet the guidelines for earthquake and high-wind loading in the International Residential Code for One- and Two-Family Dwellings, section R602. Proper bridging supports and frame supports are required.

7.b.1 Frame walls with at minimum (specify which grade) graded 2x4 lumber or functional equivalent, and either 16d hot-galvanized ring shank nails or structural screws (extra strong, thin, sharp screws that meet stringent engineering standards. Made by GRK, Spax and FastenMaster), maximum 24" on center (recommended: 16" on center ).

7.b.2 Use appropriate headers and frames for windows, doors, and other openings. If open spaces make up more than 25% of a wall, crossbeams may be required for additional support. Consult a structural engineer. (Note: structural engineers may charge about $100 or more per hour and review of plans can take four or more hours. If you're low on funds, use a standard tiny house design).

7.b.3 Double top plates are recommended but not required if engineered plans call for an alternative.

7.b.4 Sheath walls with minimum 3/8" CDX plywood or OSB (1/2" recommended), fastened with ring shank nails or structural screws, 6" on-center along the edges of the panel, and 12" on-center elsewhere. It is recommended to use adhesive on the fastener locations.

7.b.5 Sheath roof with minimum 1/2" CDX plywood or OSB (5/8" recommended), fastened with ring shank nails or structural screws, 6" on-center along the edges of the panel, and 12" on-center elsewhere. All edges of roof sheathing must be supported by either roof rafters and blocking or unsupported edges may be braced by Wood Structural Panel Edge Clips (commonly referred to as H-clips)

7.b.6 Use adhesive on all sheathing unless plans approved by an engineer do not call for it.

7.b.7 Tie the roof to the walls with hurricane straps, and tico nails or equivalent.

7.b.8 Tie the walls to the foundation/trailer frame with one of these methods:

a) hurricane tie-down brackets and minimum 3/8" galvanized bolts.

b) a threaded rod and turnbuckles from trailer frame to top of wall plate, then hurricane roof ties to tie studs, plates, and roof trusses.

c) another method that is detailed in the THOW plans and that has been reviewed and approved by a structural engineer licensed in the state in which the THOW is built.

7.b.9 For floor joists, 2x4 lumber is acceptable; 2x8 can provide greater R value.

7.b.10 When building on a trailer frame, the steel frame and crossmembers may BE your floor frame and structure. You may place the subfloor directly on trailer frame, fastening every 12" with #14 coated or galvanized self tapping metal screws. Keep in mind, this method is not in the International Residential Code. If your trailer does not have sufficient crossmembers, you may build a separate floor structure (a box floor) and bolt it to the trailer rails.

7.b.11. Light gauge metal framing, or SIPS framing or other alternatives approved by an engineer, are also acceptable in combination with wood framing when installed according to the standard.

7.c. SIPs: If Structured Insulated Panels (SIPs) are used, they must be installed according to the manufacturer's guidelines, and secured to the trailer in a similar manner as a wood frame.

7.d. Windows & other exterior glass must be tempered. or laminated, or secured with shutters during tow.

7.e. Roofs: Minimum roof slope (measured in rise over 12" run) must meet roofing material requirements. Vardo roofs are permitted.

7.f. Alternative Construction: With regards to unconventional building systems: shipping containers as an example - welding to the steel frame of the trailer is not required if ISO standard cast steel corner twist locks are present as a permanent part of the trailer

Vapor and Moisture Barriers and Venting

8.a. The THOW must be properly sealed with flashing, vapor barriers and moisture barriers:

The undercarriage must have a barrier to prevent rain splash and ground moisture from penetrating.

Exterior walls should provide a water managed system to ensure that a secondary weather barrier will enable the wall assembly to remain dry. A rain screen is code in some areas. must have a rain screen. (there also needs to be criteria describing what is a proper water-managed and pest resistant rain screen included.) Exception: if SIPs are used and the manufacturer does not recommend a rain screen, then it's not required. Alternatively build homes that are built to ensure that water does not penetrate are also excluded.

8.b. The roof must be vented. Exception: if closed cell spray foam insulation is used, a roof vent is not required.

8.c. An exhaust fan must be present in the kitchen area or bathroom. A limiter is helpful, as well as a humidistat and timer. Guidance for proper ventilation can be found in ASHRAE 62.2.

Insulation

9.a. Roof and floor insulation must be at least R19.

9.b. Wall insulation must be at least R13 (recommended: R15).

9.c. The THOW must have insulation around wheel wells and between the trailer and the floor joists, or in the case of the trailer frame being the floor structure, a layer of at minimum 1/2" insulation between the subfloor and the trailer frame is recommended to prevent thermal bridging.

9.d. Air exchangers are recommended (but not required) in tight homes to protect indoor air quality.

Water, Sewer, Gas, and Electrical Systems

10.a. Tiny house appliances and systems should must be installed with extra caulking or properly secured during travel to withstand road vibration.

10.b. Pipes must be fastened in a manner that enables them to remain securely connected during towing.

10.c. Gas connections made with threaded fittings must be made with high flexibility and high vibration resistant pipe thread compound. Inspect all gas connections for leaks prior to using system after each trailer move.

10.d. Any appliance used in, on, or attached to, the house must be UL approved, or considered safe for residential use. For the interior envelope (enclosed space) of the house, use appliances that are UL approved for interior use. An example of what NOT to attach to or use in a house would be a typical propane camp stove.

10.e. All electrical and gas systems must be provided with a way to disconnect. These systems should be turned off when the house is moved. Propane tanks must be outside the building envelope but may be stored in an isolated attached shelter on tongue or otherwise.

10.f. Heavy objects that are part of the house may need to be fastened to the structure (beyond what is normally used in a conventional house.) This includes: wood stoves, bathtubs, appliances, propane tanks, water tanks, permanently placed furniture, etc. If they cannot be fastened, they should be removed or otherwise secured when the house is moved. Refrigerators and slide-in ranges should be anchored to the wall to prevent tip-over during both moving of the THOW and avoiding potential injury while in normal use.

10.g. Drinking water must be supplied by hoses intended for such purpose, not standard garden hoses.

10.h. Water storage containers must be food grade.

10.i. Sinks, showers, and toilets must be either plumbed into holding tanks that can be emptied at an appropriate RV or marine pump out station, or plumbed into a sanitary sewer or septic system. In locations where legal, grey water systems may be substituted for irrigation or disposed of in french drains. Exception: Incinerating and composting toilets are acceptable.

10.j. Plumbing connected to sewer lines or holding tanks must be vented through either the roof or a side wall (just below the roof line with an RV wall vent cap), in accordance with NFPA 1192, Chapter 7.6. Unvented sinks are acceptable with HepVo traps. Greywater systems can be safely used without venting, though they will drain faster with vents present and will present a liability issue if sold without disclosure, and if installed in such a way that can be converted to attach to holding tanks or sewer lines, must be installed with venting as noted.

Heating Systems

11.a. Electric heating systems must be approved (UL listed) and installed in accordance with the manufacturers instructions and local codes.

11.b. Wood stoves: Wood stoves must be EPA approved and use EPA approved piping. A CO (carbon monoxide) detector is required in the general living area and each bedrooom.

There must be an exterior air inlet at or under the woodstove. This should remain completely open whenever the woodstove is (or has recently been) used.

Ventilation fans should be rated at less than 60 cfm or a limiter must be used. Fans should be turned off and a window opened if the wood stove is smoking.

11.c. Propane heaters: When a propane heater is present, propane gas detectors with electrical propane shut-off valves must be installed. A CO (carbon monoxide) detector is required in the general living area and each bedroom.

11.d. Kerosene heaters are not permitted.

Fire safety: NFPA 1192 Chapter 6 specifies fire safety requirements. They are also called out below, rephrased for THOWs.

12.a. The front door must be least 2'6" wide by 5' high.

12.b. In addition to the front door, there must be another exit on the first floor, either a door or an egress window (an opening of

at least 17" x 24" to allow for exit in case of fire).

Follow ANSI guidelines for egress. Word as follows:

There must be a primary means of escape, and at least one secondary means of escape. Each sleeping area shall have two different paths to escape to the outside of the home, where the primary means of escape is the door to the outside of the THOW. A secondary means of escape shall be as follows:

(1) It must be an outside window, outside door, or roof hatch that is located on an exterior wall other than the primary means of escape, or located in the roof, and independent of and remote from the primary means of escape.

(2) It must be operable by hand and not require the use of a key or special tool for operation from inside the vehicle.

(3) No more than 20lb of force (89 N) shall be required to open a means of escape.

(4) Means of escape, if not an exterior passage door, shall provide an opening of sufficient size to permit the unobstructed passage, with its major axis parallel to the plane of the opening and horizontal at all times, of an ellipsoid generated by rotating about the minor axis an ellipse having a major axis of 24 in. {610 mm} and a minor axis of 17 in. {432 mm}.

(5) An exterior passage door, if used for a means of escape, shall provide an unobstructed opening with a minimum horizontal dimension of 18 in. {432 mm} and a minimum vertical dimension of 48 in. {1219 mm}.

12.c. An egress window or door is required in all lofts and bedrooms. This does not follow ANSI guidelines, and egress is covered in 12b

12.d. If a loft is present, a stable means of getting to and from the loft is required but a ladder is acceptable; stairs are not required.

12.e. A smoke detector is required in the general living area and each bedroom. The smoke detectors may be battery operated or wired.

12.f. If the THOW has gas or wood burning appliances, a CO (carbon monoxide) detector is required in the general living area and each bedroom. A combination propane-CO detector is acceptable. This is stated above under Heating Systems, but repeated here to include all gas or wood burning appliances, such as cook stoves and water heaters.

12.g. A fire extinguisher should must be readily accessible and is required in homes intended for sale.

1 If you're building a tiny house that can meet the specifications above,

2 please head over to the Tiny House Registry to certify it (free of charge).

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