• Comment #1 Provides performance code language to add relocatable tiny houses to the existing Appendix BB – Tiny House Appendix

• Comment #2 Builds on Comment #1 by providing alternative prescriptive structural pathways for relocatable tiny houses

Appendix BB:

• Provides clear construction and inspection standards
• Aligns relocatable tiny houses with IRC dwelling requirements
• Reduces enforcement uncertainty

Appendix BB does not:

• Override zoning or land-use authority
• Mandate adoption
• Lower safety or habitability standards

Relocatable tiny houses provide safe, affordable, flexible housing, that expands housing choice, while allowing communities to plan proactively.

Tiny houses constructed on a chassis and used for permanent occupancy are functioning as dwelling units according to the IRC definition:

“A single unit providing complete independent living facilities for one or more persons, including permanent provisions for living, sleeping, eating, cooking, and sanitation.”

Despite this, no national model code or standard currently regulates them as dwellings for permanent occupancy.

• The U.S. Department of Housing and Urban Development (HUD) does not regulate relocatable tiny houses on wheels under its Manufactured Home Construction and Safety Standards (24 CFR Part 3280) if they meet HUD’s RV exemption criteria (built on a chassis, ≤400 sq.ft., permanently towable). In its 2018 Federal Register notice (2018-24950), HUD further clarified it does not distinguish between seasonal or permanent occupancy for RVs and that it does not intend to regulate tiny homes meeting the RV exemption criteria—even when used as year-round housing.
• Appendix BA of the IRC, which applies to manufactured housing, is only applicable to HUD-labeled units.
• Federal Motor Vehicle Safety Standards (FMVSS) and National Highway Traffic Safety Administration (NHTSA) requirements apply solely to transportation safety—not the structural, utility, or life-safety concerns related to dwellings.
• Recreational Vehicle Industry Association (RVIA) standards, including ANSI A119.5 for Park Model RVs, do not address the full range of structural, fire, life-safety, and durability requirements applicable to tiny houses used as dwelling units.
• This comment provides a path to IRC compliance for owner-builders, small builders, and nonprofits who are typically unable to afford to follow a modular regulatory path because IRC modular programs rely on factory-based manufacturing and certification programs.

The IRC is therefore the appropriate model code to regulate this housing type. Appendix BB is particularly well suited, as it has already been adopted in more than half of U.S. states and requires explicit adoption by jurisdictions. This allows communities to adopt, modify, or decline these provisions based on local needs, without imposing requirements on jurisdictions not yet ready to regulate relocatable tiny houses.

No. This is overdue. Relocatable tiny houses are already being implemented by jurisdictions nationwide, frequently through fragmented or improvised approaches. Model code language is needed to provide consistency, clarity, and safety for a housing type that people are already choosing for flexibility, environmental considerations, housing security, and affordability. This proposal brings these homes into clear regulatory alignment.

None beyond what already exists when enforcing adopted codes. When a jurisdiction adopts Appendix BB provisions, the AHJ is enforcing explicit, adopted IRC language rather than making discretionary determinations. This reduces liability by replacing ad hoc interpretations with uniform, defensible standards. The building official is authorized to regulate relocatable tiny houses as required for occupancy and only for the location of installation. Transportation, road use, and towing are outside the scope of the building code and the AHJ’s jurisdiction.

A Relocatable Tiny House is a dwelling unit, 400 s.f. or less, excluding lofts, that provides complete independent living facilities, including permanent provisions for living, sleeping, eating, cooking, and sanitation and which is integrated with an approved Federal Motor Vehicle Safety Standards (FMVSS) compliant chassis frame. They are also called Movable Tiny Houses and Tiny Houses on Wheels in existing ordinances.

When built and placed according to adopted building or zoning codes relocatable tiny homes are legal dwellings. The IRC includes Appendix BB for foundation based tiny homes. This proposal expands that appendix to provide specific provisions for relocatable tiny houses on chassis in jurisdictions who wish to incorporate relocatable tiny homes into their city planning models.

Foundation-built tiny houses are constructed directly on permanent sites and regulated under IRC provisions.

Relocatable Tiny Houses are built on a chassis system and currently fall into a regulatory gap without proposed additions to Appendix BB – Tiny Houses.

Both can meet IRC habitability and safety standards if designed under the proposed tiny house provisions.

RVs are designed for short-term, intermittent occupancy and regulated under RVIA which does not fully account for the fire and life safety concerns that IRC is intended to address. Relocatable tiny houses are designed to IRC dwelling standards for permanent occupancy.

Treating tiny houses as RVs often limits where they can be placed. Most commonly they are relegated to peripheral or campground areas which are zoned for RV use. Appendix BB clarifies the distinction, meeting IRC thresholds so that relocatable tiny homes can be zoned within existing residential zones where affordable units are most often needed.

Manufactured homes are built in accredited facilities by licensed manufacturers to the federal HUD Code. They have a minimum square foot threshold of 320 s.f.

Relocatable tiny houses are most commonly built by small builders, owner builders or non profit organizations which are diametrically opposed to compliance with federal regulations. Like all dwellings, relocatable tiny houses must comply with local building and zoning standards.

Local building departments via plan review, permits, inspections – just like any other dwelling.

Both, consistent with standard IRC practice. The unit owner is responsible for construction compliance, while the property owner is responsible for site conditions, placement, utility connections, and ongoing compliance with zoning and property regulations. This mirrors existing enforcement for accessory dwelling units, manufactured homes, and moved buildings.

• Appendix BB: Tiny houses (on foundations)
• Appendix BB (proposed): Extends coverage to relocatable tiny homes

Conventional residential codes assume larger homes, and don’t account for the unique spatial, design, and mobility characteristics of tiny houses. Specific provisions ensure safety, livability, and consistent inspections without unnecessary barriers.

Adopting ‘Appendix BB – Tiny Houses’ language into local residential codes is optional as required for your community.

Having prepared, vetted code language available allows officials to evaluate applications safely without starting from scratch.

No. Core safety, energy, and habitability standards remain intact. Scale is adjusted only to reflect smaller dwelling size. While relocatable is new in IRC it is an existing structure classification in IBC and there are already methods of inspecting and approving this classification in code bodies.

The proposed code language aligns with IRC standards for structural safety, energy, fire, and life safety. The 2016 acceptance of the Tiny House Appendix already allows for the scale-based provisions like ceiling heights, loft access, and egress and access that typically go with relocatable tiny houses, no new exceptions are being requested.

All systems must meet the same performance and safety requirements as larger homes.

Tiny houses must have smoke and CO detection, emergency escape openings and loft access meeting already approved thresholds.

Both. For building code purposes, the chassis is treated as part of the structural system supporting the dwelling. Transportation regulations govern road use. Once placed, the unit is regulated as a dwelling under the IRC, with the chassis functioning as an integrated structural component.

• Chassis design: FMVSS compliant system capable of supporting permanent occupancy loads.
• Foundation and anchoring: Secure against wind and seismic forces
• Load transfer: Proper distribution to foundation or piers/anchoring
• Utility connections: Safe attachment to water, sewer, fuel gas and electrical

This is determined by local policy and site conditions. The proposed code language does not require wheels to remain functional once placed, nor does it require they be removed, provided the unit is properly supported and anchored in accordance with approved plans.

Relocatable tiny houses may be supported by approved foundation systems including piers, slabs, helical piles, or other engineered solutions. Foundation selection is site-specific and must address frost depth, soil conditions, and load transfer.

Units must be anchored to resist applicable wind and seismic loads consistent with IRC requirements for dwellings. Load paths from the structure through the chassis to the foundation must be clearly detailed and approved.

• FEMA P-85: Design Loads for Housing
• IRC Appendix BA: Anchoring Design Considerations
• ANSI/ASTM standards for materials and construction
• Existing IRC Appendix BB provisions for structural, fire, energy, and life safety

Engineering is required when prescriptive IRC provisions are exceeded or where site-specific conditions warrant it, such as nonstandard anchoring or high wind or seismic zones. This is consistent with existing IRC requirements and does not create a new mandate unique to relocatable tiny houses.

• Floor plans, elevations, and sections
• Structural details, including chassis integration
• Foundation and anchoring details for the placement site
• Utility connection details
• Energy compliance documentation

Three inspection pathways include:

• Full Field Inspection, identical to the standard IRC inspection process, applied as the building is constructed and conducted either in person or remotely, as permitted by the receiving AHJ.
• Comprehensive Pre-Move Inspection, consistent with the IEBC provisions for moved buildings, allowing inspection of concealed work prior to relocation and a final inspection at the receiving site.
• Combination Inspection, allowing the AHJ to accept inspections from third-party electrical, plumbing, or mechanical inspectors where appropriate, followed by a final inspection by the AHJ—a practice already common for remote or owner-built construction.

Yes. Inspections may be phased, with portions completed at the construction site, remotely or in person, and final inspection conducted at the site of installation. This mirrors existing practice for modular, manufactured, and moved buildings.

At the AHJ’s discretion, and at the owners expense, ANSI-certified third-party inspectors may be used for specific trades or phases, followed by final approval by the local authority. This is consistent with existing IRC enforcement practices.

Zoning determines placement; building code determines how they’re built safely.

Yes — if the jurisdiction adopts and enforces code provisions recognizing them as dwellings, not only temporary or accessory structures.

Use classification is determined by zoning, not the building code. Appendix BB addresses how units are built safely; it does not dictate how or where they may be used.

Ownership and tenancy are regulated through zoning and property law. From a building code perspective, rental or ownership status does not alter construction or safety requirements. To ensure relocatable tiny homes address the affordability crisis, many jurisdictions now prohibit their use as short-term rentals (STRs).

Utility connections must meet IRC safety requirements. Flexible or disconnectable connections may be permitted where approved, provided they maintain safety, durability, and accessibility for inspection.

Utility abandonment follows standard local procedures. Disconnects, caps, and site restoration are handled the same way as for removed dwellings or accessory structures.

When relocated, the unit is treated as a moved building under existing IEBC provisions. Concealed work inspections may be verified prior to relocation, with final inspection and approval occurring at the receiving site. No new regulatory framework is required.

Only if they comply with IRC floodplain requirements and any applicable FEMA regulations. No exemptions are provided under Appendix BB.

Yes, there are currently several case studies of jurisdictions trying to implement relocatable tiny homes in meaningful ways. Cities like Boise, ID, San Diego, CA, Fresno, CA, the state of Maine, the state of Colorado, the state of Massachusetts among others have written in valuable code ordinances and state laws to incorporate Relocatable Tiny Homes. Unfortunately, without model code language there is very little uniformity to be found. Another reason this proposal is so timely.

Evidence from communities that have allowed them shows no measurable negative impact; properly built units enhance diversity and resilience.

Additionally, there has been significant support from existing community members who are often struggling with the affordability crisis as well. Zoning for IRC compliant relocatable tiny homes stands to offer supplemental income to existing home owners in qualifying areas by renting out a space to a relocatable tiny house.

The IRC alternative materials and methods provision (R104.11) remains available. Appeals and modifications follow standard local procedures.

For reference, the history of this Comment at the first two Code Action Hearings of this cycle are below.

CAH2

CAH1