Building an ADU in Colorado

What state law lets you build

Colorado's ADU law, HB24-1152, was signed on May 13, 2024. From June 30, 2025, every "subject jurisdiction" must allow one ADU as an accessory use to a single-unit detached house anywhere it allows those houses. The ADU can be inside the house (such as a basement unit), attached to it, or in a separate building.

A subject jurisdiction is a city or town with at least 1,000 people that sits inside a metropolitan planning organization, or the part of a county that is inside both a census designated place of 40,000 or more and a metropolitan planning organization. The Colorado Department of Local Affairs (DOLA) lists them, including Denver, Aurora, Colorado Springs, Fort Collins, Boulder, Lakewood, Pueblo, Grand Junction, Greeley, Longmont and Highlands Ranch (unincorporated Douglas County). Check the full list on DOLA's ADU law page.

An ADU under the law is a unit with "complete independent living facilities" on the same lot as a main home, with space for living, sleeping, eating, cooking and sanitation. The city does not have to allow more than one ADU per lot, but it may.

The law does not cover "exempt parcels": lots without public water and sewer (or whose well permit cannot serve another unit), historic properties outside a historic district, and lots in a floodway or 100-year floodplain. [1][2][3]

What cities can and can't require

In a subject jurisdiction, the city still applies its building, fire, utility and stormwater codes, and it can use design and size rules that are not "restrictive" under the law. But it cannot:

• Refuse an ADU between 500 and 750 square feet. It may allow smaller or larger units, and it may cap an ADU at the size of the main home.
• Require side setbacks larger than those for the main house in the same zone.
• Require a rear setback larger than the greater of 5 feet or the rear setback for other accessory buildings (such as garages) in the same zone.
• Require a bigger minimum lot for an ADU than for a single-unit house.
• Demand an architectural style, materials or landscaping stricter than for the main house, or treat factory-built ADUs more strictly than site-built ones.
• Require that you, the owner, live in the house or the ADU. The city may only ask you to show you live on the lot when you apply to build or convert the ADU (not when the ADU is built at the same time as a new house), or when you apply for a short-term rental license.

Parking: the city cannot make you build a new off-street space for the ADU. It may make you designate an existing driveway, garage or tandem space for it. It can require one new space only if all three apply: the lot has no existing off-street space, the zone required parking for the main house as of January 1, 2024, and on-street parking is banned on the block.

Fees: the city may still charge generally applicable impact fees and may ask your water or sewer provider to confirm it can serve the ADU.

Tiny homes on wheels: the city decides whether its ADU definition includes or excludes motor homes, recreational vehicles and multipurpose trailers. See our backyard tiny house guide. [1][2]

How approval works and how fast

Your ADU application must go through an "administrative approval process": city staff approve, approve with conditions, or deny it based only on objective standards in local law. It cannot require, or be bumped up to, a public hearing or a decision by a council, board or hearing officer. DOLA says words like "compatible" or "harmonious" are generally considered subjective standards, and the law allows decisions based only on objective ones.

There are two limits. If your lot is a designated historic property and the city is a certified local government, a historic preservation commission can review it. And DOLA says an appeal of a staff decision to a body such as a board of adjustment is allowed, as long as it sticks to the objective standards.

HB24-1152 does not set a number of days for a decision. Your city's own permit timelines apply. Our ADU permit process guide explains the usual steps. [1][2]

HOAs, condos and planned unit developments

In a subject jurisdiction, and in any town DOLA certifies as an ADU Supportive Jurisdiction, an HOA declaration, bylaw or rule that restricts ADUs in a way the law prohibits is "void as a matter of public policy". This applies to rules adopted before or after May 13, 2024. An HOA may still set "reasonable restrictions" that do not unreasonably raise the cost or effectively block the ADU. DOLA says an HOA may apply the same standards it uses for other accessory buildings.

A separate 2024 law, SB24-174, bars condominium and other unit owners' associations from adopting new rules after June 30, 2024 that prohibit or restrict ADUs where local zoning would allow them.

Planned unit developments (PUDs) in subject jurisdictions that allow single-unit homes cannot restrict ADUs more than the city's regular rules, and older PUD restrictions cannot be enforced in ways the law prohibits. [1][2][4]

Grants, financing and pre-approved plans

HB24-1152 created two money programs, but both run through towns that DOLA certifies as ADU Supportive Jurisdictions. To qualify, a local government must comply with the ADU law and adopt at least one supportive strategy, such as fee waivers or pre-approved plans. Any Colorado local government can apply, whether or not the law covers it.

Local grants (ADUG): DOLA gives grants to certified local governments, not to homeowners. Towns use them to develop pre-approved ADU plans, give technical help, and waive or reduce ADU fees. The law caps an award at $15,000 per ADU the local government permits, and DOLA requires a 25% local cash match. Past awards include $157,000 for Fort Collins's pre-approved ADU program and fee waivers, and $105,000 for Adams County fee waivers. Round 3 is open from September 28 to October 23, 2026. See DOLA's ADU Grant Program page.

Loans through lenders: the Colorado Housing and Finance Authority (CHFA) runs an ADU Interest Rate Buydown Program (up to $25,000 per loan to permanently lower the rate on a fixed-rate home equity loan or cash-out refinance; HELOCs do not qualify) and an ADU Credit Enhancement Program (a cash deposit of up to 10% of the loan as extra collateral). Borrowers must earn no more than 140% of statewide area median income (currently $174,440), and the ADU must be in a certified ADU Supportive Jurisdiction. You apply through a lender of your choice.

Check whether your town is certified on DOLA's ADU Supportive Jurisdictions list. As of October 9, 2026 it listed about 30 places, including Adams County, Boulder, Fort Collins, Grand Junction, Larimer County, Longmont and Westminster. Denver was not on it. Our ADU financing guide and ADU cost guide cover other options. [1][5][6][7][8][9]

Parking near transit and model codes

HB24-1304 is mainly about apartments, not ADUs. Since June 30, 2025, cities and counties in metropolitan planning organizations cannot enforce minimum parking requirements for multifamily and residential adaptive-reuse projects within a quarter mile of frequent transit stops mapped by DOLA.

HB24-1152 also told the state to write model public safety code requirements for factory-built structures, including ADUs, covering local conditions such as roof snow loads, wind and wildfire risk, for local governments to consider. DOLA also points local governments to its Template Land Development Code. [1][2][10][11]

If your city says no

Each subject jurisdiction had to file a one-time compliance report with DOLA by June 30, 2025, or by December 30, 2025 with an approved extension. A 2025 executive order tells DOLA to use HB24-1152 and related laws to identify "Strategic Growth Compliant" local governments, which get priority for certain state funding.

HB24-1152 does not create a complaint process for homeowners. If your city's code seems to conflict with the state law, you can ask the state's Division of Local Government about how the law applies at 303-864-7720 or through DOLA's ADU law page. Confirm lot-specific questions with your city's planning office. [1][2]

Where local rules differ

The state law sets a floor, and cities can be more generous. Denver, for example, allows ADUs up to 864 or 1,000 square feet depending on lot size in its single-unit districts. See our Denver ADU page for its rules, fees and permit steps. To compare other states, see Arizona and Montana. [2][12]

Colorado laws to know

• HB24-1152 (2024), C.R.S. 29-35-401 to 405

  Requires subject jurisdictions to allow one ADU with each single-unit detached home from June 30, 2025, through staff approval, and limits size, setback, parking, owner-occupancy, HOA and PUD restrictions. [1][2][3]

• SB24-174 (2024)

  Bars condominium and other unit owners' associations from adopting or amending rules on or after July 1, 2024 that prohibit or restrict ADUs the local zoning would allow. [2][4]

• HB24-1304 (2024)

  Ends minimum parking requirements for multifamily and residential adaptive-reuse projects near frequent transit in metro-area cities and counties, starting June 30, 2025. [10][11]

Questions people ask