Washington’s middle-housing law is landing, city by city

It applies to any city with 25,000 or more residents (using 2020 census data), and to some smaller cities that sit in an urban growth area next to the largest city in a county over 275,000. If your city is above 25,000 people, it must allow at least two homes per lot, and if it is above 75,000 it must allow at least four. Cities below those thresholds outside those growth areas are generally not required to change, though some choose to.

It depends on your city’s size. In cities over 75,000 people you can build at least four units on any residential lot, rising to six near major transit or if two of the units are affordable. In cities between 25,000 and 75,000 you can build at least two units, rising to four near transit or with one affordable unit. These are state minimums. Your city can allow more, but not less.

In a city over 75,000 people, you reach six units in one of two ways: build within a quarter-mile walk of a major transit stop, or make two of the six units affordable. Affordable here means rental units at 60% of area median income or ownership units at 80% of area median income. This transit-and-affordability bonus is the same structure Washington borrowed from earlier reforms in Oregon and California.

HB 1110 does not use one statewide date. Each city complies by the later of six months after its next required comprehensive plan update, or twelve months after its next implementation progress report. For the central Puget Sound counties, King, Pierce, Snohomish and Kitsap, that deadline was June 30, 2025. Other regions phase in on their own plan-update cycles through 2027. If a city misses its deadline, the state’s model ordinance takes over and overrides conflicting local rules until the city complies.

Yes. Seattle adopted interim rules that took effect June 30, 2025, and its permanent Neighborhood Residential overhaul, part of the One Seattle Plan, took effect January 21, 2026. Under the new rules Seattle allows at least four units on residential lots, and six within a quarter-mile of frequent transit. This replaced most of the city’s old single-family-only zoning.

Yes. Tacoma adopted "Home in Tacoma" Phase 2 in November 2024, which created new Urban Residential zones that replace single-family-only zoning across the city and bring it into line with HB 1110. Tacoma actually moved faster than most large cities and had its middle-housing framework in place before the Puget Sound deadline.

Spokane is on a later timeline than the Puget Sound cities. Because it is in eastern Washington on a different plan-update cycle, its compliance deadline is around 2026, roughly six months after its 2026 comprehensive plan update. Spokane got a head start with a 2022 emergency ordinance allowing fourplexes, though it reset its local maximum to four units in December 2023 after a conflict between the six-unit rule and federal mortgage-lending rules.

Much less than before, and sometimes none. Within a half-mile walking distance of a major transit stop, a city cannot require any off-street parking. Elsewhere, the city may require no more than one space per unit on lots under 6,000 square feet, and no more than two spaces per unit on lots of 6,000 square feet or larger. These are ceilings the state set to stop parking rules from blocking middle housing.

A major transit stop generally means a light rail station, a commuter rail station, or a bus rapid transit stop. Being within a quarter-mile of one raises your allowed unit count in the larger cities, and being within a half-mile removes any required parking. Because these bonuses are tied to transit, checking your distance to the nearest qualifying stop is one of the first things to do when scoping a lot.

HB 1110 covers duplexes, triplexes, fourplexes, fiveplexes, sixplexes, townhouses, stacked flats, courtyard apartments and cottage housing. The law requires these to be "compatible in scale, form and character with single-family houses," so they are low-rise, house-scale buildings rather than large apartment blocks. This gives owners a wide menu to fit the building to the lot.

It is genuinely too early to judge. Most large cities only became compliant between mid-2024 and January 2026, and permitting plus construction takes years. Tacoma’s first-year data showed most permit applications still in progress and only a small share reaching completed units, which is normal for the start of a reform. Spokane’s pre-existing 2022 ordinance put over 400 middle-housing units into the pipeline, but a statewide production total does not exist yet. Expect real numbers over the next few years, not now.

Not exactly. HB 1110 sets minimum unit allowances on residential lots, so a detached single house is still allowed. The change is that two to six homes are now also legal where only one was before. In practice, cities like Seattle and Tacoma replaced their single-family-only zones with new residential zones that permit the fuller range, so the "only one house" rule is gone even if houses themselves are not.

Start with your city’s adopted middle-housing ordinance and development code, because HB 1110 sets the floor but each city writes the detailed standards on setbacks, height and design. Many cities adapted the state Department of Commerce model ordinance, published in January 2024. The Commerce middle-housing pages and your city’s planning department are the authoritative places to confirm what applies to your specific lot.