Washington (statewide): House Bill 1110 (Middle Housing Bill)

For most of the last century, the residential land in Washington's cities was reserved by law for one detached house per lot. As the state's population grew and home prices climbed, this single-family-only rule left little room to add the smaller, lower-cost homes that fit between a house and an apartment block. By the early 2020s, lawmakers in Olympia had decided that asking cities to relax these rules one council vote at a time was too slow, and they moved to set a single statewide floor instead.

The result was House Bill 1110, formally titled 'Increasing middle housing in areas traditionally dedicated to single-family detached housing.' Governor Jay Inslee signed it on May 8, 2023, and it took legal effect on July 23, 2023. The version that became law was the Engrossed Second Substitute, meaning it was rewritten and amended several times before passing. It is now Chapter 332, Laws of 2023.

What made the bill notable was not just its content but its politics. Rather than landing as a narrow party-line measure, it cleared both chambers with bipartisan margins, passing the House 75 to 21 and the Senate 35 to 14. The design is mandatory and tiered: every city above a certain size has to comply, the exact requirement scales with population and distance to transit, and there is no opt-out for a council that would rather keep its existing rules.

The law uses a specific term, 'middle housing,' to describe the building types cities must now allow. These are the homes that sit between a single detached house and a large apartment building. The statute names nine types and requires affected cities to permit at least six of them: duplexes, triplexes, fourplexes, fiveplexes, sixplexes, townhouses, stacked flats, courtyard apartments, and cottage housing.

In plain terms, the range runs from a duplex up through a sixplex, plus rows of townhouses, flats stacked one above another, small apartment buildings arranged around a shared courtyard, and clusters of detached cottages on a single lot. The point of listing them out is to stop a city from technically allowing 'four units' but then writing design or lot rules so restrictive that only one of these forms could ever actually be built. By naming the types and requiring a minimum number of them, the law tries to keep the new density genuinely buildable rather than allowed on paper only.

Where a unit count is required, it is a floor, not a ceiling. The recurring phrase in the standards is that cities must allow the stated number of homes per lot 'unless zoning permits higher densities,' so a city that already allows more is free to keep doing so. The law sets the minimum every affected city has to reach.

HB 1110 sorts affected cities into tiers by population, using the 2020 federal census count, and then increases the requirement for lots close to high-frequency transit. The Department of Commerce identified 77 cities that the law applies to, divided across these tiers.

The largest cities, those with a population of 75,000 or more, must allow at least four units on every residential lot where detached houses are allowed. Within a quarter mile of a major transit stop, that floor rises to six units. A lot anywhere in these cities can also reach six units if at least two of the units are affordable, giving builders a path to the higher count away from transit in exchange for below-market homes.

Mid-sized cities, those between 25,000 and 74,999 people, face a lower floor: at least two units on every lot, rising to four units within a quarter mile of a major transit stop. As in the large cities, a lot can reach the four-unit count anywhere if at least one unit is affordable.

The smallest group covered by the law is made up of cities under 25,000 people that sit inside the urban growth area of a larger city. These must allow at least two units per lot, with no transit or affordable-housing bonus layered on top. Cities well below the thresholds and outside those growth areas are largely left out, which is how the law concentrates its effect on the places where most people already live and where transit already runs.

One of the most consequential parts of HB 1110 has nothing to do with unit counts. The law bars cities from imposing any minimum parking requirement on middle housing located within one-half mile of a major transit stop. In those areas a builder is free to provide as much or as little off-street parking as the market wants, rather than being forced to fit a set number of stalls per home.

This matters because parking minimums are often the rule that quietly kills a small multiplex. On a typical city lot, requiring one or two parking stalls per unit can leave no room to actually build the four or six homes the zoning now permits. Land that must be paved for cars cannot hold a building. By removing the minimum near frequent transit, the law lets the allowed density be realized instead of allowed in theory and blocked in practice. The half-mile parking zone is also wider than the quarter-mile transit zone that triggers the higher unit counts, so the parking relief reaches further out than the density bonus.

The Legislature returned to parking the following session. In 2024, separate legislation amended the state's parking rules again, broadening limits on how much parking cities can require, which builders and planners have generally read as reinforcing the direction HB 1110 set rather than reversing it.

HB 1110 does not flip on everywhere at once. Compliance is tied to each city's regular update of its comprehensive plan and development rules under Washington's Growth Management Act. A city must adopt the new middle-housing zoning by, or shortly after, the deadline for its next periodic plan update, so the dates are staggered across the state.

For the large urban counties, those deadlines fell in this window. King, Snohomish, and Pierce counties finalized their plan updates in December 2024, with the matching zoning ordinances expected by mid-2025. Seattle, for example, was required to adopt compliant zoning by June 30, 2025, and Renton carried the same deadline. Other parts of the state run on later cycles, with some updates not due until 2026 or 2027.

To keep cities from stalling, the Department of Commerce published model ordinances, with one drafted for cities of 25,000 and greater and another for cities under 25,000. These are not just templates. If a city misses its deadline without adopting compliant rules, the state's model code applies in the meantime and, as planners describe it, will supersede and override any conflicting local regulations until the city catches up. The backstop means the requirement takes effect whether or not the local council acts.

One thing to be honest about: there is no reliable statewide count yet of how many homes HB 1110 has actually produced. Because compliance is rolling and most of the big-city deadlines only arrived in 2025, the permits and completed buildings that the law enables are still working their way through design and construction. Any specific statewide unit total circulating today should be treated with caution. The law's effect on real housing numbers will only become measurable as these recently rezoned lots move through permitting over the next several years.

The bill did not pass without objection, and resistance has continued through implementation. The central complaint from many city officials is the loss of local control: HB 1110 overrides local zoning choices statewide, and councils that spent years building their own land-use plans found those plans pre-empted by Olympia. Even with bipartisan support at the state level, this top-down structure has drawn pushback from communities that feel the decision was taken out of their hands.

On the ground, the most common worries are practical ones. Critics raise concerns about increased traffic and parking demand as more units appear on streets built for single houses, and about whether existing water, sewer, and other infrastructure can carry the added density. The parking rule sharpens this debate, since removing minimums near transit is exactly the provision neighbours often point to when they fear crowded curbs.

A different line of criticism comes from housing advocates rather than opponents of density. Their concern is that allowing more units does not by itself guarantee affordable ones, and that new middle housing could still be priced out of reach for many buyers and renters. In high-cost markets, a newly built fourplex can still sell or rent at prices far above what the bill's supporters hoped to deliver. The affordable-unit bonuses built into the tiers are the law's main answer to this, but they are optional incentives rather than blanket requirements, so how much affordable housing actually results will depend on whether builders choose to use them.

For anyone watching from British Columbia, HB 1110 will look familiar, because BC passed strikingly similar legislation in the same period. The province's Bill 44, the Small-Scale Multi-Unit Housing (SSMUH) law, requires every local government with a population over 5,000 to permit small multi-unit homes on lots that were previously zoned for a single house or duplex. The base requirement is at least three units on lots up to 280 square metres and four units on larger lots, rising to at least six units on larger lots within 400 metres of a frequent transit stop. Like Washington, BC also stripped out parking minimums near transit, with no minimum parking required for projects within 400 metres of a frequent transit stop. Municipalities were required to bring their bylaws into line by June 30, 2024.

BC's companion measure, Bill 47, the Transit-Oriented Areas law, is the rough equivalent of Washington's transit tiers taken further. It requires municipalities to designate land within 800 metres of a rapid transit station and 400 metres of a major bus exchange as transit-oriented areas, then meet provincial minimums for height and density that peak nearest the station. The province estimated this could add 100,000 housing units over ten years.

The parallels are hard to miss. Both jurisdictions chose a mandatory, top-down approach with no real opt-out for local councils. Both scaled the requirement to transit, allowing more homes the closer a lot sits to frequent service. Both removed parking minimums near that transit. And both relied on a provincial or state agency to publish model codes that apply if a local government fails to comply on time. The two governments arrived at almost the same toolkit at almost the same moment.

Because the designs are so close, Washington works as a useful preview of how BC's reforms may unfold, and a reminder of where the hard parts lie. The first lesson is that passing the law is the easy half. Both Washington and BC have learned that the real test is implementation: rewriting local bylaws, clearing permits, and actually getting shovels in the ground. Washington's rollout is tied to comprehensive plan deadlines that mostly landed in 2025, which is precisely why no trustworthy statewide count of new homes exists yet. BC's timeline ran slightly ahead, with its SSMUH deadline in mid-2024, but it faces the same gap between rules changing and buildings rising.

The second lesson is that the parking and transit rules matter as much as the headline unit counts. In both places, removing parking minimums near transit is what makes the higher densities physically buildable on a normal lot. A four-unit or six-unit allowance means little if the parking rules leave no room for the building, which is why both governments paired the two changes deliberately.

The third lesson is about expectations. The criticism heard in Washington, that more units does not automatically mean cheaper units, applies just as directly in British Columbia's expensive markets. A newly permitted multiplex in a high-cost neighbourhood can still arrive at prices that strain the buyers the policy was meant to help. For builders, owners, and buyers in BC, the practical takeaway is that these reforms open real new options on ordinary residential lots, but turning that legal permission into a finished, well-priced home still depends on lot specifics, transit distance, and local infrastructure. Watching how Washington's 77 cities move from rezoning to construction over the next few years offers BC a close, comparable case to learn from.