Washington HB 1110 Middle Housing, City by City

The state rule

HB 1110 (2023, RCW 36.70A.635) sets minimum units per lot in cities planning under the Growth Management Act. Cities may allow more.

• Tier 1, population 75,000 or more: 4 units per lot; 6 within a 1/4-mile walk of a major transit stop or with 2 affordable units.

• Tier 2, 25,000 to under 75,000: 2 units per lot; 4 near a major transit stop or with 1 affordable unit.

• Tier 3, under 25,000 inside a contiguous urban growth area with the largest city in a county over 275,000: 2 units per lot.

Affordable units must stay affordable for at least 50 years under a recorded covenant, and match the other units in size and bedrooms. Cities must allow at least 6 of 9 types: duplexes, triplexes, fourplexes, fiveplexes, sixplexes, townhouses, stacked flats, courtyard apartments and cottage housing. ADUs can count toward the density.

Parking

• No off-street parking can be required within a 1/2-mile walk of a major transit stop.

• Elsewhere, no more than 1 space per unit on lots of 6,000 sq ft or less, and 2 per unit on larger lots.

• SB 5184 (2025) adds wider caps for jurisdictions of 30,000 or more, phased in from January 27, 2027.

Which lots are excluded

Critical areas and their buffers, watersheds of impaired reservoirs and urban separators are excluded. Lots under 1,000 sq ft created by subdivision do not have to reach the full density. Cities can also get extensions for displacement risk or lacking infrastructure.

Deadlines

Each city's deadline is 6 months after its periodic comprehensive plan update. For King, Pierce, Snohomish and Kitsap counties that was June 30, 2025. Clark County cities were due December 31, 2025, and the Spokane County group moved to December 31, 2026. Where a city misses its deadline, the Department of Commerce model ordinance supersedes conflicting local rules until the city adopts its own.

Related 2025 laws

• SB 5559: unit lot subdivisions reviewed administratively under clear and objective standards, so units can be sold on their own lots.

• HB 1096: an administrative split of one residential lot into two.

Cities must adopt both with their 2027 plan update, or within 2 years of July 27, 2025.

What cities adopted

• Seattle (Tier 1): interim rules took effect June 30, 2025; permanent code is Ordinance 127376. Neighborhood Residential lots allow the greater of 1 unit per 1,250 sq ft, 4 units, or 6 near transit or with 2 affordable units. No parking within 1/2 mile of light rail, commuter rail or bus rapid transit, or for units of 1,200 sq ft or less. One Seattle Plan Phase 1 (Council Bill 120993) took effect January 21, 2026.

• Bellevue (Tier 1): Ordinances 6851 and 6852, adopted June 24, 2025. Up to 4 units per lot, or 6 near major transit or with 2 affordable units.

• Tacoma (Tier 1): Home in Tacoma, effective February 1, 2025. 4 units per lot in UR-1, 6 in UR-2 and 8 in UR-3, with parking of 1, 0.75 and 0.5 per unit and none within 1/2 mile of major transit.

• Renton (Tier 1): adopted June 24, 2025. Up to 4 units per lot, or 6 within a 1/4-mile walk of major transit or with 2 affordable units.

• Kent (Tier 1): Ordinance 4517, effective July 30, 2025. Ordinance 4530, effective January 9, 2026, eases some frontage improvements for projects of 4 or fewer units.

• Vancouver (Tier 1): middle housing in the low- and medium-scale neighborhood zones; 1 to 6 units per lot use a residential building permit, and no vehicle parking is required.

• Spokane (Tier 1): Building Opportunity for Housing, effective January 1, 2024, with up to 4 units per lot in R1 and R2 and no parking within 1/2 mile of transit. The city's HB 1110 deadline is December 31, 2026.

• Shoreline: Ordinances 1026 and 1027, adopted January 13, 2025, created Neighborhood Residential 1, 2 and 3 zones.

• Mercer Island: middle housing rules effective June 30, 2025.

For each city's permit steps, see the jurisdiction breakdowns. For Seattle backyard units, see the Seattle DADU guide.

Common questions

How many units can I build on my lot?

In cities of 75,000 or more, at least 4, or 6 near a major transit stop or with 2 affordable units. In cities of 25,000 to 75,000, at least 2, or 4 with transit or 1 affordable unit. Local codes can allow more.

Can the city require parking?

Not within a 1/2-mile walk of a major transit stop. Elsewhere, no more than 1 space per unit on lots of 6,000 sq ft or less, or 2 per unit on larger lots.

What if my city has not adopted its code?

After the deadline, the Commerce model ordinance supersedes conflicting local rules until the city adopts compliant ones.

Can each unit be sold separately?

Through a unit lot subdivision. SB 5559 requires cities to review these administratively by their 2027 update or within 2 years of July 27, 2025.

How SASHKOV handles it

• Runs a yield study: how many units the lot can carry under the city's code, and whether a lot split or unit lot subdivision fits.

• Checks critical areas, utilities, access and frontage before design starts.

• Prepares the permit set and coordinates the surveyor, engineers and other licensed professionals under one contract.

Washington exempts residential buildings of up to four units from the architect requirement; above that, SASHKOV brings a licensed architect into the contract.