Building an ADU in Denver

What you can build here

Denver City Council passed the Citywide ADUs measure on November 18, 2024, and it took effect on December 16, 2024. ADUs are now allowed in all zone districts that allow new single-unit homes, about 70% of the city's land, up from 36%. The change also carries out Colorado's 2024 ADU law, HB24-1152. See our Colorado ADU law page for what the state requires.

You can build one ADU per primary home. It can be a basement or attic unit, an addition, a unit over a garage, or a backyard cottage. Behind a duplex or row house (where allowed), each unit can have one ADU, but it must be in a detached building. An ADU can have only one kitchen, and an outside stair to it cannot be on the main house's street-facing side.

Mobile homes, recreational vehicles, "tiny homes" on wheels and travel trailers cannot be used as ADUs. See our backyard tiny house guide for other options. [1][2][3]

Size, height and setbacks

Size. In single-unit (SU) districts, an attached or detached ADU can have up to 864 square feet of floor area on a zone lot of 7,000 square feet or less, and 1,000 square feet on a larger lot. In other districts, an attached ADU can be up to 75% of the main home's floor area or 864 square feet, whichever is greater. A detached ADU's footprint is capped at 864 or 1,000 square feet depending on the district and lot.

Detached ADUs follow building-form rules that depend on your neighborhood context:

• Urban (U-) districts: up to 2 stories and 24 feet, in the rear 35% of the lot. In U-SU and U-TU districts, side setbacks are 3 feet on lots 40 feet wide or less and 5 feet on wider lots. The rear setback is 5 feet, or 0 feet on an alley if garage doors don't face the alley.
• Urban Edge (E-) single-unit districts: either 1 story and 17 feet, or 2 stories and 24 feet, in the rear 35% of the lot. Side setbacks are 3 or 5 feet by lot width. The rear setback is 5 feet, except a two-story ADU needs 12 feet where no alley or street abuts the rear lot line.
• Suburban (S-) single-unit districts: either 1 story and 17 feet, or 2 stories and 24 feet, in the rear 50% of the lot. Side setbacks are 3 feet (lots 25 feet wide or less), 5 feet, or 7.5 feet (lots 62 feet wide or more). The code lists a 10-foot rear setback for a one-story ADU and 20 feet for a two-story one.

Rear setbacks: what the state law says and what Denver's code says. HB24-1152 says a covered city may not require a rear setback for an ADU larger than the greater of 5 feet or the rear setback required for other accessory buildings in the same zone district. Denver's code lists a 10-foot (one-story) or 20-foot (two-story) rear setback for a detached ADU in S- single-unit districts, and a 5-foot rear setback for other detached structures, such as garages and sheds, in those districts where no alley abuts the rear lot line. The city's sources don't say how it squares the two. Ask CPD Residential Review which rear setback it will apply on your lot.

A 2023 city guide says a detached ADU isn't allowed without waivers or variances if your zone lot doesn't meet Denver's minimum zone lot standards. Confirm your exact limits with CPD. [3][4][5][6][7][8]

Parking and driveways

Denver dropped minimum car parking requirements citywide on August 11, 2025, and even before that, parking minimums did not apply to ADUs. You don't need to add a parking space.

An ADU cannot have its own driveway separate from the main home's, unless it is a new access from an alley. A detached ADU takes vehicle access from the alley, or from the street when there is no alley. [2][3][4][9]

Fees

Denver charges by project valuation. Check the CPD fee schedules for your numbers. The main city fees for an ADU are:

• Building permit fee: for work valued $100,001 to $500,000, $770 for the first $100,000 plus $5.60 per additional $1,000. For $50,001 to $100,000, it is $420 plus $7 per additional $1,000.
• Plan review fee: 50% of the building permit fee.
• Zoning construction permit fee: for $50,001 to $100,000 of valuation, $100 plus $0.50 per $1,000 in valuation; over $100,000, $150 plus $0.50 per $1,000 in valuation.
• Address: $60 per address. Every ADU needs its own.
• Card payments: a 2.5% service fee; none for e-check.

Affordable housing linkage fee: ADUs are on Denver's list of exceptions. You submit plans showing the structure is an ADU and that the existing building is the primary structure.

Water and sewer: Denver Water says you "may need a new water supply license" and "will owe an additional system development charge". A noncopper service line must be replaced from the main. Your ADU also needs a sewer use and drainage permit.

Construction waste: ADUs over 500 square feet need an approved waste diversion plan and a refundable performance security deposit before the building permit is issued.

For budgeting the whole project, see our ADU cost guide. [2][10][11][12]

Timeline

Denver does not publish a fixed review time for ADUs. It posts estimated review times, based on the last 90 days, on its Average Plan Review Times dashboard, updated daily. The dashboard groups single-family and duplex projects such as a new home or an addition over 400 square feet as "Major Residential". Projects are reviewed in the order received.

Uploading everything for zoning, building and sewer permits at once gets a simultaneous review. Trade permits wait until the residential construction permit is issued. See our ADU permit process guide for the general sequence. [2][13]

Owner occupancy, HOAs and PUDs

In single-unit districts, at least one owner must live in the existing main house as their primary residence when the ADU permit application is filed. You prove it with two documents such as a driver's license, vehicle or voter registration, tax documents or a utility bill. This doesn't apply when you build the house and ADU at the same time. After the permit, the ADU can keep being used even if you move out.

Note: an older section of the city's Citywide ADUs page still says the owner "MUST live on the property". That conflicts with the current zoning code (Section 11.8.2.2.B), which requires it only when you apply.

Denver does not review HOA rules. Under state law, HOA rules that restrict ADUs in ways HB24-1152 prohibits are void in Denver, though reasonable restrictions are allowed. Since February 20, 2026, Denver's code treats any Planned Unit Development that allows single-unit homes as allowing ADUs, and old PUD bans on ADUs are not enforced. [1][2][3][7][14][15]

Garage conversions

Denver's 2023 ADU code update removed zoning barriers to converting existing structures, such as garages, into ADUs. A 2023 city guide says an existing structure can be converted even if it doesn't meet the detached ADU building-form rules, but any addition must meet them. The same guide warns that the structure must meet building and fire codes for foundations, energy, utilities and fire separation, and that "most residential garages built on concrete slabs cannot be legally converted." Ask CPD Residential Review about your garage before you design. Removing a structure needs a demolition permit. See our garage conversion guide. [1][2][8]

Renting it out and selling

Renting for fewer than 29 nights at a time needs a short-term rental license, and the property must be your primary residence. Renting for 30 days or more needs a residential rental property license. See Denver's short-term rental rules.

You cannot sell an ADU separately. Denver says an ADU "is not considered a separate property that could be sold on its own", and in single-unit districts it must stay under the same ownership as the main house. [1][3][16]

Financing and local programs

Colorado's ADU loan programs through the Colorado Housing and Finance Authority (rate buydowns and credit enhancement) are only for ADUs in DOLA-certified ADU Supportive Jurisdictions. Denver was not on DOLA's certified list as of October 9, 2026, so check again before you apply. See our ADU financing guide for other options.

Denver is also working on Unlocking Housing Choices, a zoning project to allow more middle housing in residential neighborhoods. The proposals are still drafts. To compare another state's rules, see our Phoenix ADU page. [17][18][19]

Permit steps in Denver

1. Check your zoning and lot

   Look up your zone district and lot on the city's development services map. Your zone district sets the ADU's height, setbacks and placement, so confirm it before you design. [2]

2. Hire a licensed contractor and design to the zoning code

   Homeowners cannot apply for ADU permits, so you need a licensed contractor. The design must meet the Denver Zoning Code and building codes. [2]

3. Get historic approval first, if it applies

   In a historic district or on a landmark you need a certificate of appropriateness from Landmark Preservation, and the city recommends getting it before applying. See ADU design review for landmark properties. [2]

4. Prepare your plans

   Upload a scaled site plan with lot lines, existing buildings, the ADU's height and distances, and water and sewer lines; building elevations; and building plans with structural details. Add a property survey if you build within three feet of a property line. [2]

5. Apply online in e-permits

   In e-permits, choose "building log", then Single Family/Duplex Residential and New Accessory Dwelling Unit. Upload everything for the zoning, building and sewer use and drainage (SUDP) permits at once to get a simultaneous review. [2]

6. Sort out address, water and waste plans

   The ADU needs its own address. Denver Water may require a new water supply license and charge an additional system development charge; see its ADU page. ADUs over 500 sq ft need an approved waste diversion plan and a refundable deposit before the building permit is issued. [2][10][12]

7. Pull trade permits

   Electrical, plumbing, mechanical and roofing permits are separate. Since May 22, 2025, they require an issued residential construction permit first. [2]

8. Pass inspections and get a Certificate of Occupancy

   Schedule construction inspections as you build. No one can live in the ADU until it has a Certificate of Occupancy. [2]

Who to call

• CPD Residential Review (Detached Homes and Duplexes)

  Zoning and building plan review questions for single-family and duplex projects, including ADUs

  720-865-2710

  [20]

• CPD E-permits Help and Permit Intake

  Help applying in e-permits; email planreview@denvergov.org

  720-865-2720

  [20]

• CPD Permit Counter and Cashiering

  In-person help (book an appointment) and fee payment, Monday to Friday 8 a.m. to 4 p.m.

  Wellington Webb Municipal Building, 201 W. Colfax Ave., 2nd floor, Denver, CO

  [10][20]

• Denver Water Sales Administration

  Water supply licenses, taps and system development charges for ADUs

  303-628-6100

  [12]

• Office of the City Forester

  Required if there are trees in the public right-of-way or protected trees in the front or side-street setback

  (720) 913-0651

  [2]

Questions people ask