01
Confirm the local rules
Identify the city or county, review current zoning and determine which local middle-housing requirements apply.
A homeowner’s starting guide
HB 1110: what Washington’s middle-housing law could mean for your lot.
The law changed how many Washington cities plan for housing choices. What may be possible on a specific property still depends on local rules and the site itself.
Ask about your propertyThe short version
More housing choices are part of the plan.
Washington’s HB 1110 (2023) requires certain cities to plan for and allow middle housing in areas traditionally reserved for detached single-family homes. “Middle housing” can include forms such as duplexes, triplexes, fourplexes, townhouses, stacked flats and cottage housing.
The law’s requirements vary by jurisdiction, and local governments implement them through their own development regulations. The state Department of Commerce publishes model ordinances and guidance, but local standards and site conditions still determine what can be proposed on an individual lot.
That means a zoning label or statewide headline is not a complete feasibility answer. Lot dimensions, access, critical areas, utilities, setbacks, parking and other standards can affect a concept. A property-specific review can help identify what needs to be checked before making a larger investment.
What owners can do
Turn a policy change into a property decision.
02
Look at the whole site
Check lot size, access, conditions and development standards, not only the broad zoning designation.
03
Compare realistic options
Consider whether keeping the existing home, adding units, or redevelopment best fits the property and your goals.
Explore local rules
King County cities and middle-housing resources.
Select a highlighted city on the map or use the city list. Links go to the best available official city page on middle housing or local code. Where a city has not published a dedicated HB 1110 page, the link goes to its official zoning or planning resource; the status of local implementation can change.
Map boundary data: King County GIS, Incorporated Areas of King County. This map is for general reference and does not establish zoning or parcel jurisdiction.
Official information
Read the state guidance.
This page is general information, not legal, architectural, engineering, tax, investment or permitting advice. Laws and local regulations may change; verify current requirements with the relevant jurisdiction.