On Tuesday, Boulder County commissioners voted 2-1 to approve stricter limits on the size of new homes and additions in unincorporated parts of the county, despite a unanimous recommendation from the county planning commission to deny the changes.
The new rules — which some commissioners and staff see as a way to curb rising home sizes and environmental impacts as well as maintain neighborhood character — will go into effect May 13, when a moratorium on home builds over the median implemented in January will also be lifted.
Previously, homes could be built up to 125% of the neighborhood median size, and owners could request additional square footage through the site plan review process. People who asked for additional square footage were approved 91% of the time, according to staff.
Commissioners and staff see the new regulations as a way to remove some of that uncertainty and discretion with a more straightforward cap.
Nationwide, new home sizes have stayed roughly stable since 2010. New homes in Boulder County have grown 11%, from an average of about 3,500 square feet that year to roughly 3,900 in 2023. When basements, porches and garages were included, Boulder County new homes averaged more than 4,700 square feet in 2023.
About 30 people spoke at the public hearing, with the majority opposing the changes. In March, following a four-hour public hearing, the Boulder County Planning Commission unanimously recommended against new size caps and lift the moratorium.
Commissioner Claire Levy dissented, citing inequities created by the new approach.
“I’m concerned … about disparity across neighborhoods in Boulder County … and the fact that people in neighborhoods with large homes get to build large homes," she said.
A sliding scale will allow for additional allotments above the median for additions and rebuilds (but not new builds on vacant lots). For example, if an existing home is under 1,500 square feet, property owners are allotted an additional 1,000 square feet regardless of the neighborhood median. Existing homes between 3,001 and 3,500 square feet can be rebuilt with an additional 675 square feet. Homes larger than 4,501 square feet cannot be rebuilt larger than the neighborhood median.
Homes in Allenspark, Eldora, Eldorado Springs, Raymond and Riverside are limited to 1,500 total square feet for new builds, rebuilds and additions, which is over the median for all of those townsites, according to a county staff person.
“[M]any of the parcels in these areas can be challenging to develop larger structures on, and the existing stock and character tends to be smaller,” county planner Ethan Abner wrote in an emailed response to followup questions.