Accessory Structures in Longmont, CO (2026)
3 verified accessory structures rules for Longmont, Colorado, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Longmont allows one accessory dwelling unit per single-family lot, sized between 500 and 800 square feet, with its own setback and building-permit requirements under the Land Development Code.
Longmont ADU Size and Placement Standards
Some RestrictionsLongmont Municipal Code § 15.02.080.E.3.b
b.Number and size of accessory dwelling units.i.Limit per lot: Only one ADU is allowed per lot, in addition to the principal single-family detached dwelling.ii.Minimum and maximum size: Regardless of the principal dwelling's size, an ADU may be between 500 and 800 square feet.iii.Maximum size exception: An ADU may be larger than 800 square feet if the proposed ADU does not exceed 50 percent of ...
ADU Rental Restrictions
Longmont bars accessory dwelling units from being used as short-term rentals outright, under Longmont Municipal Code section 15.02.080.D.2.c. A separate ADU standard in section 15.02.080.E.3.g also blocks selling an ADU apart from the main house, keeping accessory units tied to long-term, owner-linked occupancy rather than the short-term rental market.
Longmont Bans Short-Term Rentals in ADUs
Heavy RestrictionsLongmont Municipal Code § 15.02.080.D.2.c; E.3.g
c.Accessory dwelling units shall not be used as a short-term rental. ... g.Limit on sale, tenancy and occupancy.i.Accessory dwelling units shall not be sold separately from the principal dwelling.
Shed & Carport Rules
Longmont exempts small detached accessory structures, tool sheds, storage sheds, playhouses and similar buildings, from a building permit only when they are one story and the floor area is 200 square feet or less. Anything bigger triggers a full building permit under the 2024 International Residential Code as amended by the city, plus the zoning setback rules that apply to accessory structures on the lot.
Longmont Shed Permit Exemption Rule
Some RestrictionsLongmont Municipal Code § 16.06.060
Section R105.2 of the International Residential Code is amended by the revision and deletion of the following subsections listed under Building: Subsection 1 is replaced with the following: 1. One-story detached accessory structures used as tool and storage sheds, playhouses and similar uses, provided that the floor area is 200 square feet (18.58 m 2 ) or less.
Looking for Boulder County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Longmont city rules.
Accessory Structures in Boulder County →