1 county-level rule, plus city-specific rules for 2 cities in Jefferson County, Colorado.
Verified from official government sources
Jefferson County allows one Accessory Dwelling Unit per single-family lot in Agricultural and Residential (R, MR, SR) zones under Section 19 of the Jefferson County Zoning Resolution. Detached ADUs require a 7,500 sq ft minimum lot. Maximum size scales by lot size from 600 to 1,200 sq ft. Owner-occupancy is required (one of the two units). Colorado HB24-1152 (effective 6/30/2025) preempts certain rules in subject jurisdictions.
2 cities in Jefferson County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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Jefferson County Ordinance Hub →