Accessory Dwelling Units (ADU’s)

What’s an ADU?

ADU stands for Accessory Dwelling Unit, and is sometimes known by the terms “carriage home” or “mother-in-law” apartment.  An ADU is a small living unit that can be added to a single family home, either detached or attached, provided that the home owner resides on the property and all other zoning, size and design regulations are met.

Why Do We Allow ADUs in Golden?

  • Many other communities, including Arvada and Grand Junction, have adopted ADU ordinances to provide their citizens with additional housing options
  • Provide a housing option that is more affordable for those who want to live in a single family neighborhood
  • Offer an option that supports special family needs (such as care for a senior family member who also desires independence).
  • Allow extra income for homeowners, by helping to offset the cost of a home in their desired neighborhood.

Before You Build an ADU:

Step 1

Read all the information from Section 18.28.240 of the Municipal Code to learn all the rules and regulations regarding ADU’s

Some important things to note are: the property owner on record must occupy the principal dwelling or accessory unit, one parking space must be provided for the unit, and no more than three persons shall occupy an accessory dwelling unit.

Any additional unit will require a Residential Allocation Application, available on our Online Permitting System,  to be filled out and submitted to the Planning Department before any building permits are granted for your property.

Step 2

Check your zoning using the Parcel Information Map to see if ADU’s are allowed in your zone district. ADU’s are allowed in conjunction with all single-household detached dwellings in residential zone-districts. (R-E, R-1, R-1A, R-2, R-3).

Step 3

Make sure your lot follows the following criteria:

  • R1, R2 and R3 minimum lot size is 7000sqft
    • Lot coverage of all accessory structures must not exceed 10% of the lot area
  • ADU’s must follow the appropriate frontages, setbacks, design criteria and more –

Visit our Zoning Regulations Page for more on zoning information, or refer to our Zoning Information Sheet pdf download for specific regulations on every zoning district

Internal ADU’s are now permitted to occur on an entire floor of a multi-floor home, and no longer are required to comply with specific square footage requirements.

Step 4

Sometimes, basement finishes or addition designs that raise the issue of creating a new dwelling unintentionally come through the Planning Division and Building Division. Building components that trigger the discussion of making the space into a legal Accessory Dwelling Unit are things such as a stove top and kitchen in tandem with a full bathroom and bedroom. If these components are part of a design, it triggers full compliance with ADU regulations and the signing of the ADU Deed Restriction pdf download.

If you intend to design in this manner, adding anything except a stove top is allowed within the existing unit, but you are then required to sign a Declaration of Use pdf download to be kept on file with the City of Golden. This agreement would state that you do not intend to lease out or separate your new living space from the existing residence.

All new detached ADU additions require fire sprinklers within the newly constructed space. The only exception to this rule is the conversion of a basement. If you have any specific questions regarding fire sprinkling, feel free to contact the building department at 303-384-8151.

Call the Planning Division with further questions at 303-384-8097 or email us at

COG Mesa

 Did You Know?
Golden was originally chosen as the territorial capital of Colorado in 1862.

Additional Resources

City of Golden, Colorado
COG Mesa
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