Arapahoe County is one of several counties in the metro area jumping on the latest trend and tool to increase housing availability.

On Wednesday, the county’s Board of Commissioners voted to approve accessory dwelling units (ADUs) in unincorporated areas of Arapahoe County. Commonly called “granny flats” or “mother-in-law apartments,” ADUs are smaller, independent living quarters either attached to a single-family home or located on the same lot as the main house.

According to the American Planning Association, the construction of ADUs and zoning reform, like the change approved in Arapahoe County, are a key “weapon” in increasing the affordability of residential neighborhoods in an effort to combat rising housing costs across the U.S.

“ADUs can help with affordability,” Arapahoe County Commissioner Jessica Campbell-Swanson said via press release. “We heard from residents across the county this is an option that residents have been waiting for.”

Responding to voiced concerns, Campbell-Swanson referred to a comparative analysis that showed ADUs do not reduce property values or overextend infrastructure capacity; based on the county’s requirements, these structures will maintain community characteristics.

Earlier this month in neighboring Denver, new rules also took effect regarding ADUs. After more than a year working with a community advisory committee, technical experts, neighborhood organizations, Denver City Council members, and the public worked to develop zoning code changes for accessory dwelling units (ADUs).

ADUs are currently allowed in portions of Denver (based on permitting and neighborhood zoning laws), Aurora, Bennett, Cherry Hills Village, Englewood, Littleton and Sheridan. 

“These are going to be legitimate structures,” Campbell-Swanson added, citing the requirements the regulations have in place for design and size. “I don’t share the concern ADUs will stretch capacity or change the character of a neighborhood.” 

Arapahoe County began exploring adding ADUs to the County Land Code in the fall of 2021 and has engaged residents throughout the regulatory process. Feedback from residents and stakeholders was presented to the County’s Planning Commission, who recommended ADUs be allowed only on lot sizes 19 acres and bigger.  

Commissioners disagreed, citing an urgent need to allow the structures on smaller property sizes, down to 5,000 square feet. With the 19-acre recommendation, 977 lots within unincorporated Arapahoe County would have been eligible for an ADU compared to about 18,000 lots that meet the 5,000 feet requirement.  

ADUs are often used as auxiliary housing for extended family members, or as rental units whether traditionally or on online platforms such as VRBO or AirBnb.

 “We want all our neighbors to be comfortable,” Arapahoe County District 4 Commissioner Leslie Summey said. “It’s reassuring to know that the data on ADUs points to increased property values and positive outcomes for property owners and communities.” 

The new ADU regulations encompass elements designed to ensure successful implementation:  

• Arapahoe County will permit both attached and detached ADUs in all agricultural and most residential zoning districts on lots that are at least 5,000 square feet.  
• In urban areas, on lots of less than 19 acres, ADUs can have up to two bedrooms. Detached ADUs are required to be situated in the rear or side yard, behind the principal dwelling.   
• Square footage limitations will be based on lot size and/or the size of the principal dwelling.   
• Minimum design requirements, off-street parking, and owner occupancy of either the principal dwelling or the ADU will also be mandatory.   
• Exceptions to ADU location, square footage, and bedroom limitations will be granted for properties of 19 or more acres.   
• Homeowner association-managed neighborhoods may prohibit ADUs through private covenants.  

Arapahoe County’s new ADU regulations will go into effect on Sept. 12.