Longmont, CO Accessory Structures: Tiny Homes (2026)

Longmont adopts the International Residential Code through LMC Title 16, including IRC Appendix Q, which sets standards for dwellings 400 square feet or less in floor area excluding lofts (minimum ceiling heights, loft access by ladder or alternating-tread device, emergency escape and rescue openings). A site-built tiny home on a permanent foundation in a residential zone is either: (1) the principal single-family dwelling, in which case it must meet the dimensional standards for the zone — including the residential lot's minimum setbacks (R-SF: 15 ft front, 5 ft side, 20 ft rear without alley) and minimum lot area for the zone; or (2) an ADU under LMC § 15.02.080.E, in which case it is capped at 800 sq ft (or 50% of the principal dwelling), the owner must live in the main house or the ADU, the ADU cannot be sold separately, and it must connect to the principal home's water and sewer. Tiny homes on wheels classified as recreational vehicles, park model RVs, or trailers are not permitted as a primary or accessory dwelling in Longmont residential zones — they may be stored on private property subject to RV-storage rules but cannot be lived in. Permanent placement of a manufactured tiny home requires HUD-code certification and the same building permit, foundation, utility-connection, and inspection process as any single-family residence.