Accessory Dwelling Units (ADUs)

Accessory Dwelling Unit (ADU)

An Accessory Dwelling Unit, or ADU, is a permanently constructed dwelling unit that is either: (a) detached from the primary residence, or (b) within or attached to the primary residence or an accessory building such as a detached garage. ADUs must be located on the same lot as the primary residence. ADUs include living, sleeping, eating, cooking, and sanitation facilities as well as an entrance independent from those of the primary residence. 

Click this link for more information: Accessory Dwelling Unit Homeowner Guide

Beginning July 1, 2025, under new state regulations, ADUs cannot be prohibited by existing or future homeowners’ associations or planned unit developments. Neighborhood associations, metro districts, and other architectural review authorities may still require approval of plans; consult your neighborhood regulations prior to applying for a building permit.

The City Council has waived impact fees for ADUs as part of an on-going strategy to reduce the costs to add ADUs in the City.  The following table is a guide to how ADUs are regulated in the city: ADU Reference Table

Factory-Built Accessory Dwelling Units

 The City of Brighton supports the use of factory-built accessory dwelling units (ADUs).  Factory-built ADUs are available in two forms: US Department of Housing (HUD) certified manufactured homes, and Colorado Division of Housing certified complete prefabricated homes.

 Construction and Cost

Factory-built ADUs are constructed in a factory then transported to the property site and installed onto a foundation.  This process can be faster and more efficient than traditional on-site construction, as well as can be a more affordable option compared to custom-built units, though prices vary based on size, features, and finishes.

 Some ADU manufacturers may offer a turn-key service where they build the entire project, including the foundation and utility connections.   Whether the manufacturer provides this service or not, the foundation must be designed by a licensed engineer and be permanent, meaning it is embedded and anchored to resist downward loads and uplift forces.  The Brighton Building Division of the Community Development Department can answer questions regarding permanent foundations.

 Selecting a Factory-Built ADU

Although factory-built, the ADU will still need to comply with the City of Brighton design regulations as well as those of any community design authority such as a homeowners association (HOA).  Any needed HOA or similar review approval should be obtained prior to applying for a building permit.

 A web search will return many manufacturers that are either located in the Front Range area or will deliver here.  Make sure they are able to provide you with the home’s certification, either from HUD or from the State of Colorado.

 Financing

Some manufacturers also provide financing options to help homeowners manage the costs of building an ADU.   Mortgage companies and banks may offer home equity loan products that can be used to add ADUs.  The Colorado Department of Local Affairs offers resources and guidance for homeowners interested in ADUs, including information on financing available from the Colorado Housing and Finance Authority.

 Permitting

Applying for a factory-built ADU permit is like that for a unit built on-site.  However, rather than submitting architectural and structural plans, the ADU certification, either from HUD or the State, is needed.  A plot plan, soils testing report, foundation plan, and water/sewer service utility letter are also required.  HUD and State certified ADU permit applications do not require IECC or conventional heat loss calculations.  Please contact the Brighton Building Division of the Community Development Department regarding the valuation of your ADU project; the valuation is used to calculate the plan review fee, permit fee, and the use tax.

 Although full structural and architectural plans are not required for HUD and State certified ADU permit applications, to-scale elevation drawings are needed.  These drawings are used by the Planning Division to ensure compliance with the Brighton ADU design standards.

ent Code.  For assistance, please call 303-655-2072.