Boulder, CO Accessory Structures: Tiny Homes (2026)
Tiny home rules in Boulder, CO, covering tiny houses on wheels (THOWs), park model RVs, and tiny home on foundation builds, determine where they are legal and how they get permitted.
Key Facts
- Governing section
- BRC § 10-5.5-2(jj), Appendix BB
- Foundation rule
- Permanent foundation required
- Utility connection
- Permanent utility connection required
- Wheeled units
- Not covered as a code dwelling
- Off-site built units
- Follow C.R.S. § 24-32-3311(6)
- Adopted base code
- 2024 International Residential Code
Summary
Boulder allows site-built tiny houses as single dwelling units under Appendix BB of its Residential Building Code, BRC 10-5.5-2(jj). The catch: a tiny house must sit on a permanent foundation and connect permanently to utilities like any other dwelling, so a tiny house on wheels doesn't qualify as a code-compliant dwelling under this appendix. Off-site built tiny houses follow a separate state manufacturing statute instead.
(jj)Appendix BB, "Tiny Houses," is hereby repealed and reenacted to read as follows: APPENDIX BB TINY HOUSES The requirements of Appendix BB to the 2024 edition of the International Residential Code of the International Code Council shall hereby be complied with which appendix is hereby adopted by reference as part of the City of Boulder Residential Code and have the same force and effect as though fully set forth in this subsection, except as specifically amended by the provisions of this subsection. BB101.1 "Scope" is hereby repealed and reenacted to read as follows: This appendix shall be applicable to site built tiny houses used as single dwelling units. Tiny houses shall comply with this code except as otherwise stated in this appendix. Tiny houses shall be on permanent foundations and permanently connected to utilities, as required by this code. Tiny houses constructed off-site shall be built and installed in accordance with C.R.S. § 24-32-3311(6).
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Municipal Code: Supplement 167 Update 3).
Full Breakdown
5-2(jj) repeals and reenacts Appendix BB, 'Tiny Houses,' of the 2024 International Residential Code as part of the City of Boulder Residential Code, with the same force and effect as though written directly into the Boulder Revised Code. 1, 'Scope,' as reenacted, limits the appendix to site-built tiny houses used as single dwelling units, and states that tiny houses must comply with the rest of the residential code except where the appendix says otherwise. 1 requires tiny houses to be on permanent foundations and permanently connected to utilities, just like any other code-compliant residential structure, which rules out wheeled or skid-mounted units as a qualifying 'tiny house' dwelling under this appendix.
§ 24-32-3311(6), Colorado's factory-built structures statute, rather than the on-site appendix. 5-2), a tiny house built under this appendix is also subject to the same permitting, plan review, energy code, and inspection requirements as any other detached one- or two-family dwelling in the city; there is no separate expedited or reduced-fee track carved out for tiny houses.
Violations & Fines
Constructing or occupying a tiny house that doesn't meet Appendix BB's permanent-foundation and utility-connection standard, or that skips the required building permit and inspections under Chapter 10-5.5, is a code violation prosecuted the same as any unpermitted residential construction: civil penalties starting at $150 for a first offense, rising to $1,000 for a third, plus possible criminal prosecution and a stop-work order until the structure is brought into compliance or removed.
Frequently Asked Questions
Can I live in a tiny house on wheels in Boulder?
What building code applies to a tiny house in Boulder?
Does a factory-built tiny house follow the same Boulder rules as a site-built one?
Sources & Official References
Other rules in Boulder
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