Colorado ADU Eligibility Checker

How Colorado ADU Eligibility Works

Colorado has no statewide ADU mandate. HB 1152 (2024), the state's most significant housing-mandate bill in recent memory, passed with middle-housing provisions but did not produce the clean statewide ADU right that advocates sought. As a result, every Colorado property's eligibility depends on three factors: (1) your specific city's or county's ordinance, (2) local overlay zones like historic districts or environmental sensitivity zones, and (3) your HOA's CC&Rs. The calculator reads Colorado as yellow for most properties because the correct answer is 'look up your city's ordinance,' not a clean yes or no. For the four major Front Range cities — Denver, Boulder, Fort Collins, Colorado Springs — specific ordinance paths exist and the calculator's eligibility logic factors in zoning type to give a reasonable default.

City-By-City: Where Colorado ADUs Are Legal

Denver's 2023 zoning code update expanded ADU eligibility to most residential zones in the city, including many SU (single-unit) and TU (two-unit) districts. Denver's ADU ordinance is among the most permissive in Colorado. Boulder allows ADUs in most single-family zones with additional design review and neighborhood compatibility requirements — eligibility is real but the process is longer. Fort Collins has a permissive ADU ordinance with reasonable processing times. Colorado Springs allows ADUs in several residential districts with a conditional use permit. Aurora and Lakewood have more limited ADU allowances. Resort towns — Aspen, Vail, Breckenridge, Telluride, Crested Butte, Steamboat Springs — typically allow ADUs only as part of an employee-housing or affordable-housing mitigation program that deed-restricts the unit to qualifying local workers at below-market rents. That structure materially changes what the investment looks like.

HOAs and Mountain Overlays

Colorado has no state-level preemption of HOA restrictions on ADUs. The Colorado Common Interest Ownership Act (CCIOA, C.R.S. 38-33.3) gives HOAs broad enforcement authority over CC&Rs, and HB 1152 did not carve out an ADU exception. If your HOA's CC&Rs prohibit accessory dwellings, second residences, or rentals, you're effectively blocked without a CC&R amendment. In mountain resort towns, layered environmental rules (wildfire hazard zones, avalanche zones, wildland-urban interface) can further constrain buildable envelope even where zoning allows ADUs. The Marshall Fire (2021) and subsequent wildfire-zone code updates have pushed Boulder County and other Front Range jurisdictions to stricter ignition-resistant construction requirements that affect ADU design and cost. None of these block ADUs outright but they do add meaningful design constraints.