In 2024 Colorado passed HB24-1152, a state law that overrides local ADU bans in certain places. It did not apply everywhere, and in Boulder County that distinction decides a great deal.
Who the law covers#
Coverage is narrow and specific: Cities of 1,000 or more people in a metropolitan planning area, and county land only inside a census-designated place of 40,000 or more.
Read that second clause carefully, because it is the one that matters locally. Unincorporated county land is covered only when it sits inside a census-designated place of 40,000 people or more. No part of unincorporated Boulder County meets that bar, so No. HB24-1152 does not cover this land, so the county Land Use Code governs.
The City of Boulder is a different story. It is on the state's list of subject jurisdictions, and its rewritten rules apply to ADUs proposed on or after March 8, 2025.
What covered jurisdictions must allow#
Where the law applies, the requirement is concrete: One internal, attached or detached ADU wherever single-unit detached homes are allowed, by administrative approval against objective standards and with no public hearing.
"Administrative approval against objective standards" is the heart of it. A covered city has to write down what it wants, then approve anything that meets those written standards. It cannot route an ADU through a discretionary hearing where neighbors argue and a board decides.
What covered jurisdictions cannot require#
The law also names things a covered jurisdiction may not demand: No new parking space and no owner occupancy, with limited exceptions; ADUs of 500 to 750 sq ft must be allowed; factory-built ADUs cannot be treated more strictly than stick-built.
The parking clause removes what had been the most common practical blocker: a requirement to add an off-street space, which on a small lot can be impossible. The factory-built clause matters if you are considering a modular unit, because it stops a jurisdiction treating one more harshly than a site-built equivalent purely for being factory-built.
What they can still require#
The law is not a blanket exemption from local rules. Short-term rental regulation, building, fire and utility codes, proof of water and wastewater capacity, and generally applicable impact fees.
So a covered city can still hold you to its building code, its fire code, and proof that water and wastewater can serve the unit. It can still regulate short-term rentals, which the City of Boulder does: Banned for both the ADU and the main house, unless the ADU and its rental license predate February 1, 2019.
HOAs#
Where the state law applies, it reaches private covenants too: An HOA in a state-covered jurisdiction cannot prohibit ADUs; reasonable restrictions are allowed.
"Reasonable restrictions" is doing real work in that sentence. An HOA can still have something to say about design, materials and placement. What it cannot do, in a covered jurisdiction, is ban ADUs outright.
Outside covered jurisdictions the protection does not automatically follow. For unincorporated Boulder County, whether it applies depends on a status we are still confirming: Being confirmed with State of Colorado.
Supportive jurisdictions and financing#
The state created a second, voluntary tier. A jurisdiction can be certified as an ADU Supportive Jurisdiction, and that certification unlocks financing for homeowners: Homeowners in certified ADU Supportive Jurisdictions can use CHFA ADU finance programs through participating lenders.
We are confirming where the City of Boulder stands on this: Being confirmed with State of Colorado. Until that is confirmed, treat any claim about state ADU financing in Boulder as unverified.
Where to go next#
See how this plays out in practice on the City of Boulder hub, or read why unincorporated Boulder County sits outside the law and what its rewrite is considering.