ADU – Accessory Dwelling Unit | Denver Zoning Changes

If you’ve been thinking about constructing an Accessory Dwelling Unit (ADU) in Denver, keep in mind the city made several updates to the Denver Zoning Code in July 2023 that make planning a new ADU more favorable.  Here is a summary of the significant changes:

New Zone Districts were added that allow for the construction of ADU building forms, particularly in Suburban neighborhoods. The specific min lot size and length dimensions were adjusted to be more flexible for inclusion of an ADU. Specific Text from the Proposed Amendment to Zoning:

“Note: This text amendment proposes to add several new zone districts that would allow ADUs, as shown in red underline in the table above. The ADUs in Denver project will not propose to rezone any properties to these new zone districts. They will, however, be available for property owner or City Council-initiated rezonings in the future to allow such rezoning proposals to preserve context-appropriate standards for their neighborhoods, such as minimum lot size or limitations on home occupations.”


The habitable area of the dwelling, living portion of an ADU is no longer limited to 75% of the building footprint. Depending on the building configuration, you might have an 800SF dwelling that sits on top of an 800 SF garage space below, with consideration for exterior stairs and the area that counts towards the max allowable footprint of 864 SF on certain zone lots.

The bulk plane height was increased to 12’ on lots 40’ or less in width. This used to be 10 ft which was more restrictive for planning options in the (U-) Urban Zoned Districts.

Setbacks are also more favorable for planning options in the (U-) Urban Zoned Districts. The rear setback can go to zero, or lot line if no garage door faces the alley. The side setbacks are the same as required for the primary structure setback.

Perhaps one of the more exciting and significant updates to the Zoning requirements is that decks and balconies on a detached ADU are permitted to up to 100SF max (allowance) when overlooking the public alley.

The Building Coverage Exemption is now allowed for ADUs that are single story at grade and are not designed to sit above a garage use.

Another significant update that opens the opportunity for many homeowners with existing structurally sound garages is the conversion of existing garages to an ADU building form. Previously, unless the garage conformed to all ADU building form zoning requirements, the conversion or adaptation of the building to an ADU was not permitted.

Roof dormer encroachments are conditionally allowed to penetrate the Bulk Plane.

Other use standards in the (U-) Urban Zoned Districts that were adjusted include:

  • Maximum Structure Length of 36’ was removed.
  • Maximum floor area increased on single unit lots 6,000SF or less to 864SF.
  • ADUs accessory to two-unit and multi-unit primary uses are now allowed.

Keep in mind, Denver continues to require owner occupancy in single-unit zone districts with clarification on the definition of ownership.

Most of the changes were focused on the (E-) Urban Edge, (S-) Suburban, and (U-) Urban zoned districts. If you are considering the addition of an ADU to your property, please contact ArcWest so we can review the applicable requirement for your specific address within the assigned city zoning district.

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