HB 1337

Key Takeaways

• HB 1337, enacted in 2023 as chapter 334, Laws of 2023, is codified at RCW 36.70A.680 and RCW 36.70A.681.
• Cities and counties planning under the Growth Management Act must allow at least two accessory dwelling units on lots in zoning districts inside an urban growth area that allow single-family homes.
• The mandate reaches only the portions of towns, cities, and counties that are inside a designated urban growth area. Rural land outside a UGA is not covered.
• A city or county may not require the owner to live in the accessory dwelling unit or in the principal home on the same lot, and may not charge impact fees above 50 percent of what the principal unit would pay.

What It Means

HB 1337 is the 2023 Washington statute that took away most of the tools local governments used to say no to accessory dwelling units. It was enacted as chapter 334, Laws of 2023, and its two operative sections are codified at RCW 36.70A.680 and RCW 36.70A.681. Under RCW 36.70A.696, an accessory dwelling unit is a dwelling unit located on the same lot as a single-family housing unit, duplex, triplex, townhome, or other housing unit: a backyard cottage, a converted garage, or a basement apartment with its own kitchen and bathroom.

Before HB 1337 a Washington city could allow accessory units on paper and then make them impossible in practice, through owner occupancy rules, added parking mandates, small floor area caps, and impact fees priced like a full house. The statute removes those levers one at a time and sets a floor of two accessory units on qualifying lots.

For a broker this is listing and buyer information, not trivia. The Zoning answer for a client asking whether a lot will support a rental cottage now starts with the state floor, and the local code has to bend to it. How much that changes a given deal still depends on the market, which our look at King County versus the rest of the state puts in context.

How It Works in Washington

RCW 36.70A.680(1)(a) requires cities and counties planning under the Growth Management Act to adopt these rules into their development regulations, zoning regulations, and other official controls, to take effect at the same time as the jurisdiction's next periodic Comprehensive Plan update under RCW 36.70A.130. Subsection (1)(b) is the teeth: in a jurisdiction that has not adopted them, the state requirements supersede, preempt, and invalidate any conflicting local development regulations. Subsection (2) sets the boundary, because the rules apply only in the portions of towns, cities, and counties that are within urban growth areas designated under the chapter.

RCW 36.70A.681 supplies the specifics. Subsection (1)(c) requires at least two accessory dwelling units on all lots located in all zoning districts within an urban growth area that allow for single-family homes. Subsection (1)(b) bars any owner occupancy requirement. Subsection (1)(a) caps impact fees at 50 percent of the fees imposed on the principal unit. Subsection (1)(f) forbids a maximum gross floor area below 1,000 square feet. Subsection (2)(a)(i) bars off-street parking requirements within one-half mile walking distance of a major transit stop. Subsection (1)(k) is the one brokers should memorize: a city may not prohibit the sale of a Condominium unit independently of a principal unit solely because that unit was originally built as an accessory dwelling unit.

Private restrictions get their own section. RCW 64.38.160, in the version effective until January 1, 2028, provides that the governing documents of homeowners associations created after July 23, 2023, and applying to property inside an urban growth area may not impose restrictions on an accessory dwelling unit that the city itself would be barred from imposing. That reaches new associations, so older recorded Covenants Conditions And Restrictions Cc R are a separate legal question. Our roundup of 2026 statutory changes for Washington brokers sets this beside the rest of the housing legislation.

Example

Nadia Brooks owns a 6,200 square foot lot in a single-family zone inside the Tacoma urban growth area. The bus stop two blocks away runs fixed route service every 12 minutes for six hours across the weekday peaks, which meets the major transit stop definition in RCW 36.70A.696(8)(e). Nadia wants to build a 900 square foot detached cottage in the back yard and rent it out.

Her plan used to have three problems under the old local code: a rule that the owner had to live on site, a required added off-street parking stall, and an 800 square foot cap on detached accessory units. HB 1337 removes all three. RCW 36.70A.681(1)(b) means the city cannot require Nadia to occupy either home, so she may rent both. Because her lot is within one-half mile walking distance of that transit stop, RCW 36.70A.681(2)(a)(i) means no off-street parking stall can be required. And RCW 36.70A.681(1)(f) means the city cannot cap the cottage below 1,000 square feet, so 900 square feet clears.

The money follows the same pattern. If Tacoma would charge $12,000 in impact fees on a new principal house, RCW 36.70A.681(1)(a) caps the impact fees on Nadia's cottage at $6,000. That one subsection is worth six thousand dollars to her project budget, which is the kind of number a listing broker should be able to explain on a lot walk.

Common Mistakes and Exam Traps

• HB 1337 applies only inside designated urban growth areas. A question about a rural lot outside the UGA is not governed by the two unit floor in RCW 36.70A.681.
• HB 1337 is the accessory dwelling unit law. HB 1110, passed the same year, is the middle housing law covering duplexes, triplexes, fourplexes, and cottage clusters, and it is the one built on city population tiers of 25,000 and 75,000 in RCW 36.70A.635.
• Owner occupancy is the rule the statute killed. RCW 36.70A.681(1)(b) bars a city from requiring the owner to live in either the accessory unit or the principal home, so an answer that keeps an owner occupancy condition is wrong.
• HB 1337 did not void covenants that already existed. RCW 64.38.160 reaches the governing documents of homeowners associations created after July 23, 2023, so an older recorded restriction is a separate question.