Accessory Dwelling Unit (ADU) FAQ

What is an ADU?

An Accessory Dwelling Unit is a second dwelling unit that is in addition to the principal dwelling (main home) on the property. Accessory units are commonly referred to as granny flats, carriage houses and in-law suites.

  • There are 3 types of accessory dwelling units in the Town of Windsor:
    • Detached dwelling, which is a dwelling that is detached from the principal dwelling. This type is often associated with detached garages or in the rear of the lot.Type 1 Exhibit
    • An additional dwelling unit within or attached to the principal dwelling locked off from the primary and typically including a separate entrance. This type is often in a basement, upstairs, side or rear of a home.Type 2or3 Exhibit
    • An additional dwelling unit within or attached to the principal dwelling that is not locked off from the primary and occupants live together as single unit. This type is usually in a basement, upstairs, side or rear of home.  

Who can have an ADU?

  • ADUs are allowed on lots that are 6,000 sq. ft. or larger and that currently or will concurrently have a detached single-family home built upon them and that are located in zone districts that allow for detached single-family homes. Some HOAs may not allow for ADUs, in which case an ADU would not be permitted.

What are the steps?

  • Staff recommends starting with a concept plan. This process does not require a fee and can be completed without an engineer or architect (See the concept application for further information). After a concept review with staff, applicants would need to submit a complete ADU application and complete the review process before submitting a building permit application.

What is required for review?

  • An ADU application and site plan drawings stamped by a Colorado licensed surveyor or engineer (produced by an engineer or architect is recommended) are required for the ADU review. These drawings are required to show parking, distances to buildings and lot lines and any proposed construction. If it is a proposed ADU within the principal dwelling and the footprint of the home is not changing, a plan showing the interior of the ADU portion and an exhibit showing the parking space is needed instead of a full site plan. A current recorded deed and a narrative describing the proposed ADU are also required.Site Plan Layout 3

What is the cost for review?

How long does the review take?

  • The review process is an administrative process that may take one to three months depending on review comments to be addressed and applicant’s response time to comments. Hiring a professional architect or engineer will help facilitate a quicker approval process.

Important things to consider?

  • Does your HOA allow for ADUs?
  • Is there enough space to meet open space and setback requirements with an additional unit on the property?
  • Is there an existing parking space to meet criteria or room for an additional parking space on the lot?
  • The living space of an ADU is not allowed to be larger than the living space of the principal dwelling and must be between 500-950 square feet in size.