The City of Brighton has completed an update to the Land Use & Development Code regulations regarding accessory dwelling units, or ADUs. In compliance with a 2024 Colorado House Bill, the property owner is no longer required to occupy either the ADU or the primary home. Removing this requirement provides an opportunity to increase the supply of rental units in the city. Other barriers that had restricted the addition of an ADU have also been removed.
Residents interested in adding a detached ADU to their property may find factory-built ADUs more cost effective than built-in-place units. Factory-built ADUs are available in two forms: US Department of Housing (HUD) certified manufactured homes, and Colorado Department of Housing certified 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 more affordable 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 (a vehicle axle and jack stands do not qualify). 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, and all approvals including by the City of Brighton should be obtained prior to purchasing the unit.
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. Also, have the manufacturer verify that the ADU building can be attached to a permanent engineered foundation.
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 done through the OpenGov system and is like that for a unit built on-site. However, rather than submitting architectural and structural plans, the manufacturer’s 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. 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. Please see the Community Development webpage for more details.
Please contact the Brighton Building Division at 303-655-2017 or 1stop@brightonco.gov regarding the valuation of your ADU project; the valuation is used to calculate the plan review fee, permit fee, and the use tax. For information on other fees due upon issuing a permit and for general questions, contact the Community Development Department at 303-655-2072 or abesch@brightonco.gov.