Accessory Structures in Boulder County, CO (2026)

1 county-level rule, plus city-specific rules for 2 cities in Boulder County, Colorado.

Verified from official government sources

Note: These county rules apply to unincorporated areas of Boulder County. If you live within an incorporated city, that city's own rules apply — see the city list below.

ADU Rules

Unincorporated Boulder County permits accessory dwellings under Boulder County Land Use Code Article 4 (specifically 4-516). Following the Marshall Fire, the county adopted an expedited Disaster Recovery Unit allowance up to 900 sq ft (Resolution 2022-062). Colorado HB24-1152 (signed 5/13/2024, full compliance deadline 6/30/2025) preempts local ADU bans in subject jurisdictions, but only applies to municipalities of 1,000+ inside an MPO and certain large county census places.

ADU Rules in Boulder County

Some Restrictions

Full ordinance details →Official source ↗

Accessory Structures by City in Boulder County

2 cities in Boulder County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.

LongmontPop. 98,885

5 verified rules • ADU Rules, Carport Rules

Boulder

9 verified rules • ADU Impact Fees, ADU Owner Occupancy

All Boulder County ordinances

See every category we cover for Boulder County — parking, noise, fences, fires, animals, pools, and more.

Boulder County Ordinance Hub →