Altona, CO

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.

Unincorporated Boulder County enforces the 2021 International Residential Code (IRC) Appendix G as adopted in the Boulder County Building Code Amendments effective March 31, 2025. Pool and spa barriers must be at least 48 inches high (and not greater than 54 inches at the top), with self-closing, self-latching gates and openings that will not pass a 4-inch sphere. Colorado has no state-specific pool barrier statute; local IRC adoption controls.

Colorado allows only state-permissible fireworks (cylindrical/cone fountains, sparklers, snakes, ground spinners) under CRS 12-28-101 et seq. - all aerial and explosive fireworks are illegal statewide. Boulder County is high wildfire risk, and the Sheriff or Board of County Commissioners frequently enacts Stage 1 or Stage 2 fire restrictions under Ordinance 2023-1 and CRS 30-15-401(n.5)(II), which ban ALL fireworks in the affected unincorporated areas. Violations are civil infractions punishable by fines up to $500.

Boulder County Ordinance 92-28 sets residential noise limits of 55 dB(A) from 7:00 AM to 7:00 PM and 50 dB(A) from 7:00 PM to 7:00 AM in unincorporated areas. Lawnmowers and power tools under 5 hp are permitted 7:00 AM to 10:00 PM under CRS §25-12.

Boulder County Ordinance 2022-8 does not require dogs to be on a leash in unincorporated areas — instead, off-leash dogs must remain under voice and sight command of the handler. All dogs must wear a rabies tag and ID tag, and households are limited to 7 dogs and cats combined.

Unincorporated Boulder County allows fences up to 6 feet without a building permit under the Land Use Code. Fences over 6 feet require a permit from Community Planning & Permitting, and any fence in a 100-year floodplain needs a Floodplain Development Permit regardless of height.

Boulder County has participated in the FEMA National Flood Insurance Program (NFIP) since 1974 and enforces a Floodplain Overlay Zoning District covering the FEMA-mapped 1% annual chance (100-year) floodplain plus county-adopted floodplains for streams like Boulder Creek and the St. Vrain. The county holds a Community Rating System (CRS) Class 5 rating, giving NFIP policyholders in unincorporated areas a 25% premium discount.