The Boulder City Council is set to vote Thursday, Jan. 9 on zoning reforms that could pave the way for potentially thousands of new housing units by easing restrictions on converting single-family homes into duplexes or triplexes.
The proposed ordinance is the latest effort by councilmembers to loosen zoning rules in an attempt to lower the city’s housing costs. One of the goals is to increase the amount of “middle housing” — a housing type like duplexes, triplexes and townhomes that are typically more affordable than single-family homes. Currently, middle housing makes up just 9% of Boulder’s housing stock, according to city officials.
One key change targets mixed-use neighborhoods near downtown, including parts of Whittier and University Hill. The ordinance proposes reducing the minimum lot area per dwelling unit in the RMX-1 zoning district from 6,000 square feet to 2,500 square feet to allow for greater housing density.
These changes would not alter the height, massing or setbacks of existing homes. The goal, according to city officials, is to allow property owners to convert single-family homes into duplexes or triplexes within the existing building footprint.
Another significant proposal focuses on lower-density neighborhoods near public transit. These zoning districts — RR-1, RR-2 and RL-1 — cover parts of Newlands, Old North Boulder and much of South Boulder. While a 2023 zoning reform allowed duplexes in these areas, stringent minimum lot size requirements, such as 14,000 square feet for a duplex, often made development of multifamily housing unfeasible.
The new ordinance would allow duplexes within 350 feet of a bus corridor regardless of lot size, while retaining limits on floor area ratios, building coverage, height and setbacks. This means property owners could still increase the number of units, but the overall building footprint, including its height, would likely have to remain the same.
The ordinance also seeks to accelerate the development of affordable housing by exempting 100% permanently affordable housing projects from site review, a review process involving the Planning Board and Boulder City Council that often delays projects and adds uncertainty for developers.
City officials estimate the proposed reforms could theoretically enable the creation of up to 15,000 additional housing units, though full adoption by property owners is unlikely. The changes have the potential to make a dent in Boulder’s housing shortage, estimated at more than 10,000 homes, according to recent estimates.
John Herrick is a reporter for the Boulder Reporting Lab. His work frequently appears on-air at KUNC 91.5 FM and online at KUNC.org. Contact John at john@boulderreportinglab.org.