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Accessory Dwelling Units (ADU)

What is an “ADU”?

An Accessory Dwelling Unit, or ADU, is the industry term for what’s often called a “carriage house”, a “granny flat” or a “mother-in-law apartment".  An ADU is a small living unit that can be added to a single-family home or a duplex, either detached or attached, provided that the homeowner resides in one of the units and all other zoning, size and design regulations are met.

If your building project provides for a separate living space that includes a kitchen (with a stove top and oven), a full bathroom, and a bedroom together in the same space, you’ll need to follow specific ADU rules, and you'll need to complete an ADU Deed Restriction form.

Sometimes, we see plans that accidentally include an ADU because of these features. If your project adds new spaces but you're not planning to create a separate dwelling (for example, you're just adding a kitchen but no new bedrooms or bathrooms), you can still proceed. However, if you're adding another stove and don't plan for it to be a separate living space, you'll need to fill out a Declaration of Use form. This form confirms that you won't rent out or legally separate this part of your home as a different dwelling.

For new, detached ADU constructions, remember that fire sprinklers are required in the new space, and the utilities must connect back to the main house. The only exception is when you're converting a basement into living space.

In short, if you're adding or expanding parts of your home with these specific features, it's important to understand and follow the ADU guidelines to ensure everything is up to code and registered correctly with the City of Golden.

Why Do We Need/Allow ADU Construction in Golden?

Accessory Dwelling Units serve different needs in our community:

  • Provides a housing option that is more attainable for those who want to live in a mostly residential neighborhood, but aren’t in a position to buy a house and/or don’t need the square footage of a multi-bedroom home.
  • Offers an option that supports special family needs, such as caring for an elderly relative.
  • Allows extra income for homeowners by helping to offset the cost of a home in their desired neighborhood. 

How to Plan Your ADU

Read all the information from Section 18.28.240 of the Municipal Code to learn the rules and regulations regarding ADUs.


Important things to note:

  • The property owner on record must occupy the principal dwelling or accessory unit as their primary residence.
  • One (1) parking space must be provided for the unit.
  • No more than three (3) people can occupy an accessory dwelling unit.
  • Proof of the primary residence is required.
  • If a proposed ADU is detached or expanding on an existing structure, it must meet all zoning regulations that apply to that property (also called “form type requirements”).
  • Check your zoning using the Residential Form Zone Map to see if ADU’s are allowed in your zone district. ADUs are allowed in conjunction with all single-household detached dwellings in residential zone-districts (R-E, R-1, R-1A, R-2, R-3).
  • Make sure your lot follows the following criteria: 
    • Any ADU must meet the same development standards required in the applicable form type.
    • Lot coverage of all accessory structures must not exceed 10% of the lot area.

For more on zoning information on Accessory Dwelling Units, see Municipal Code Section 18.28.240

For information on properties within the Form Zone Overlay District, see Municipal Code Section 18.29.

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