Accessory Dwelling Units (ADU)

An Accessory Dwelling Unit (ADU), sometimes called an "in-law apartment" or "carriage house," is typically an additional housing unit within, or on the same lot as, a single-family home with entries and amenities that are separate from the primary residence. Please review the information below to see what's required for different types of ADUs before submitting your application.

Getting Started

Review the list of required documents and steps below before beginning the application process. Once you are ready to apply, you will login to our permitting system, Arvada Permits, enter the required information and upload PDF plans and related documents to your application. Utilize the eTRAKIT Online Application.

Types of Accessory Dwelling Units

The City of Arvada has two categories for Accessory Dwelling Units (ADU):

Type A

An Accessory Dwelling Unit that is detached from the principal dwelling. It is considered lockable and rentable.

Type B

An Accessory Dwelling Unit with the following characteristics:

  • Located inside a single-family dwelling, or
  • Attached to a single-family dwelling
  • Whose occupants and the occupants of the principal dwelling do not live together as a single household unit and which is rented.
  • Typically have a separate access from the principal dwelling that is locked off from the principal dwelling.

Both Type A and B Accessory Dwelling Units are considered a separate dwelling unit from the principal dwelling under the building code. Fire separation from the primary dwelling and a separate HVAC system are required. Water and sanitary sewer service for ADUs must be connected to the service lines of the primary dwelling unit and may not have separate services.

If your home is part of a Homeowner's Association (HOA) you must gain approval from the HOA in addition to permits and approvals from the City of Arvada. An approval and permit issued by the City of Arvada does not overrule HOA approval.


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Required Submittal Documents

Permit applications that are submitted with complete information will be reviewed. If you have questions about items that are required please email Building Permits Division.

Please provide each plan set individually in separate PDFs. Foundation and structural plans must be stamped by a professional licensed in the State of Colorado (engineer or architect)

Plans must include pertinent design information that includes wind speed design, snow load, and frost depth.

Plans included in package:

  • Architectural plans, Elevations, Cross Sections, and Electrical.
  • Plot Plan detailing: size, setbacks, lot coverage, landscaping, and parking.
  • Grading Plan
  • Utility Plan
  • Gas line calculations
  • Structural plans, stamped and signed by an engineer
  • Foundation Plans, stamped and signed by an engineer
  • Truss specification package, stamped and signed by an engineer
  • Soils report, stamped and signed by an engineer
  • Manual J, D, and S calculations
  • RESCheck or HERS Rating calculations, if performance energy path is utilized
  • Declaration of Covenants (obtain from Planning)
TypeReview Time Required
A3 Weeks
B1 to 2 Weeks


Fees are charged based on the complete contract value or on the square footage, whichever valuation is greater. A permit for an ADU will include a Building Permit Fee, Use Tax Plan review fee, and recording fees. Depending on the project you may also have fees for Plumbing, Mechanical, and Electrical. You can get an estimate on your fees by clicking on the "Fee Calculator" button below. Please be aware that additional fees may apply and will be identified through the permitting process.

Use the Fee Calculator.

Permit Issuance & Inspections

Once the ADU permit application has been reviewed and approved by Building, Planning, and Engineering, the permit will be ready to be issued. The applicant on the permit will be notified via email when the permit is ready for payment. All fees must be paid and the applicant must download the proper permit documents to have available on site. Fees can be paid online using a credit card. If another type of payment is requested, please visit the Building Counter to make a payment.

Please note that after permit issuance, the primary residence and ADU will be re-addressed as Unit A and Unit B respectively.

ADUs must be connected to the utilities of the principal dwelling unit and may not have separate services. Upon completion of your ADU, you may be assessed the Metro Wastewater District Fee. This fee must be paid before a CO will be issued.

Use this link to view the current fee amount.