Commonly known as the Middle Housing Bill or Missing Middle Housing Bill, HB 1110 requires cities to authorize minimum housing development densities and permit specific “middle housing” types in any zone that allows for detached single-family residences (RS zones). Middle housing includes housing types that fall between detached single-family residences and larger apartment complexes, such as duplexes, triplexes, fourplexes, townhouses, stacked flats, courtyard apartments and cottage housing. The requirements vary based on city population and do not apply to urban unincorporated areas such as Esperance.
Cities with populations between 25,000 and 75,000 residents (such as Edmonds) must allow a minimum of two units per lot that permits detached single-family residences. That is increased to four units per lot in two instances: if the lot is located within one-quarter mile walking distance of a bus rapid transit station along Highway 99 or the Sounder station or if at least one affordable housing unit is provided for a minimum of 50 years.
Cities with populations over 75,000 are required to allow a minimum of four units per lot for most lots, which is increased to six units per lot for the two situations outlined above. Earlier versions of HB 1110 required a minimum of four units per lot for smaller suburbs such as Edmonds, but that was later reduced to three units per lot before ultimately being approved at the adopted two units per lot.
“For most of the city,” Levitan wrote, “this is essentially a ‘duplex bill,’ with duplexes or two-unit townhouses required on most RS-zoned lots. For those areas that must allow at least four units per lot, HB 1110 requires the city to allow at least six of the nine middle housing types identified in the bill.” Cities may allow ADUs to achieve the minimum-density requirements, he noted.
Minimum-density requirements are not required for lots designated with critical areas and their buffers and certain watersheds listed as impaired or threatened. “Additional guidance is needed from the Washington State Department of Commerce on requirements for lots with minor critical area encumbrances (such as one small corner of a lot with a wetland buffer) that could otherwise accommodate two units on the lot; the city expects additional guidance later this year,” Levitan wrote. HB 1110 also allows cities to use an alternative density requirement for at least 75% of lots in the city that are primarily dedicated to detached single-family residences.
The bill also notes that cities:
1) May only apply administrative design review for middle housing;
2) May not required standards for middle housing that are more restrictive than those for detached single-family residences;
3) Must apply the same development permit and environmental review process that apply to detached single-family residences;
4) Must allow zero lot line subdivisions;
5) May not require off-street parking within a half-mile walking distance of a major transit stop (bus rapid transit station or Sounder station); and
6) May not require more than one off-street parking space per unit on lots smaller than 6,000 square feet and two off-street parking spaces per units on lots larger than 6,000 square feet.