Accessory Dwelling Units

Frequently Asked Questions on Accessory Dwelling Units

How many Accessory Dwelling Units can I have, and how big can an Accessory Dwelling Unit be?

On properties with zoning that include single-family residential uses, property owners may have a maximum of one (1) accessory dwelling unit.  Any ADU can be up to 500 square feet in size. ADUs that are larger than 500 square feet are restricted to 50% of the principal dwelling unit’s footprint (excluding garage, porch, or similar areas) or 800 square feet, whichever is less.

Are there owner residency requirements if I add an ADU on my property?

No, any property owner may add up to one (1) ADU to any eligible property. 

How will utilities be provided?

Accessory dwelling units must tie into the principal dwelling unit’s water and sewer connections, and will not require separate water or sewer taps, or water or sewer licenses. You will need to contact other utility providers for applicable telephone, television, electrical, gas and internet service to determine how those utilities can be served.

What if my principal dwelling unit uses an on-site wastewater treatment system (septic tank)?

If your home uses an on-site septic system, you will need to coordinate with the Health Protection Division of Health and Human Services to determine if your on-site wastewater treatment system has adequate capacity or needs to be modified in order to accommodate the proposed accessory dwelling unit. They can be reached at publichealth@broomfield.org or at 720-887-2220.

Are there design requirements for my ADU?

Accessory dwelling units shall be designed to be consistent with the design of the principal dwelling unit. Depending on the zoning of the property, the ADU may be required to meet applicable design requirements. ADUs planned on a property with no specific design standards are required to be clad in a material similar to the principal structure.

How many parking spaces do I need for an Accessory Dwelling Unit?

No new parking is required for an accessory dwelling unit except when both of the following conditions are met:

• The adjacent streets do not allow on-street parking, and
• The ADU is not located in a Parking Reduction Area (PRA). Please contact planning@broomfield.org for more information about PRAs.

If these two conditions apply, the applicant will need to demonstrate that the property will provide at least three (3) off-street parking spaces (two [2] for the primary unit and one [1] for the ADU in a garage and/or driveway).

Does an Accessory Dwelling Unit need to meet setbacks?

Accessory dwelling units must meet applicable setback requirements for the zone district of the property, except that the side setback for an ADU is never greater than the side setback for a principal dwelling unit on the same lot.

Reviews and Permits Required

A building permit for Accessory Dwelling Units is required. Use the Building Department's General Permit Application form.

• Contact the Building Division to determine what supporting documents will be required as part of your building permit submittal.
• Property owners will be required to submit an ADU Checklist as a supporting document with their Building Permit application.
• Property owners will be required to record a Declaration of Use which will state the size and location of the accessory dwelling unit and shall reference that the accessory dwelling unit must remain in compliance with the regulations contained within the Municipal Code.

Please contact your HOA before submitting a building permit.

Please also see this Accessory Dwelling Unit Frequently Asked Questions handout.