Middle Housing Updates: King, Pierce & Snohomish Counties

December 31, 2024 marked the deadline for King, Pierce and Snohomish Counties to complete their periodic updates to their comprehensive plans. Where this may have otherwise gone by without much fanfare, the changes to the housing and land use elements in many jurisdictions are causing quite the uproar. What the angry constituents on Nextdoor and at the City Council meetings don’t know is that many cities don’t have a choice. These changes are required by HB1110 and HB1337, which were both passed by the State of Washington and signed into law by Governor Inslee last year. Both bills are aimed at the expansion of middle housing options.

HB1110 requires certain cities and urban growth areas (UGAs) to allow duplexes, fourplexes and sixplexes (within 1/4mi of transit). The breakdown looks like this:

• Cities with a population over 75,000 people: fourplexes everywhere, sixplexes within 1/4mi of major transit stops if two units are affordable

  • Seattle, Tacoma, Bellevue, Kent, Everett, Renton, Federal Way, Kirkland, Auburn and Redmond are all over 75,000 people. Marysville is very close.

• Cities with a population over 25k and under 75k: Duplexes everywhere, fourplexes within 1/4mi of major transit stop if one is affordable

  • This list is much longer - Marysville, Sammamish, Shoreline, Burien, Bothell, Lynnwood, Edmonds, Lake Stevens… Check your population here

• Cities under 25k in a UGA with the largest city in the county over 275k: duplexes everywhere

  • This really only applies to King County, but a shocking amount of King County is in a UGA

There is also an “alternative compliance path” for the bill as well, which allows the exclusion of critical areas, areas with high displacement risk, or lack of infrastructure. This bill also lifts parking mandates within a half mile of a major transit stop and caps parking mandates on lots under 6,000sf.

HB1337 is perhaps more exciting to me, since it addresses accessory dwelling units (ADUs), both attached and detached. These add housing while often preserving the existing structure. Cities and counties planning under the growth management act are required to, among other things:

• Allow at least two ADUs (attached or detached) per lot on all lots within UGAs that currently allow single-family homes

• Remove or not impose owner-occupancy requirements

• The maximum ADU square footage must be 1,000sf or greater

• ADUs must be allowed to be sold as condominiums

• New HOAs cannot prohibit ADUs required under HB1337

There are additional regulations as well that address impact fees, street improvements and parking. The UGAs largely cover the cities and surrounding areas in King, Snohomish and Pierce Counties.

Incremental development is a key and historically underutilized tool towards starting to alleviate the housing crisis. Though, unless specifically required, these are not likely to be affordable units, the new housing that is allowed under HB1110 and HB1337 will incentivize higher density in areas that are closer to transit, making better use of our existing infrastructure. Especially when accompanied by a pre-approved detached ADU (DADU) program, infill housing can be built more quickly than apartment buildings, and can be done by smaller crews, allowing more developers to enter the industry. Infill development alone is not the answer to our housing crisis, but it’s time to embrace it as a major and necessary part.