HB 1337 explained for Spokane homeowners

Short answer: HB 1337 is the 2023 Washington law (RCW 36.70A.681, in effect since July 23, 2023) that requires Spokane-area jurisdictions inside the urban growth area to allow up to two ADUs per single-family lot, drop owner-occupancy requirements, permit an ADU of at least 1,000 square feet, and cap ADU impact fees at half of what the main home would pay. Here is what it changes for your lot, cited to the statute.

What HB 1337 is

HB 1337 is a 2023 Washington law that directs cities and counties planning under the Growth Management Act (GMA) to update their ADU rules so accessory dwelling units are easier to build. It is codified mainly at RCW 36.70A.680 and RCW 36.70A.681 and applies inside urban growth areas. The goal is more housing options on existing residential lots.

What HB 1337 requires

The following come from the statute itself. Local code carries the exact implementing language, so each jurisdiction page cites the local section.

• At least two ADUs per lot in urban growth areas. On lots that allow single-family homes, jurisdictions must permit two ADUs, as one attached plus one detached unit, or two detached units (RCW 36.70A.681(1)(c)).
• No owner-occupancy requirement. A city or county may not require the owner to live in the ADU or in another unit on the lot (RCW 36.70A.681(1)(b)).
• No off-street parking near major transit. A jurisdiction may not require off-street parking for an ADU within one-half mile walking distance of a major transit stop (RCW 36.70A.681).
• Size floor. A jurisdiction may not set a maximum ADU size below 1,000 square feet, so an ADU of at least 1,000 square feet must be allowed (RCW 36.70A.681(1)(f)).
• Height floor. A jurisdiction may not limit ADU roof height below 24 feet, unless the limit on the principal dwelling is lower (RCW 36.70A.681(1)(g)).
• Impact fees capped. ADU impact fees may not exceed 50 percent of the fees that would be charged for the principal unit (RCW 36.70A.681(1)(a)).
• No required street improvements. Street improvements may not be required as a condition of permitting an ADU (RCW 36.70A.681(1)(l)).

Where HB 1337 applies: urban growth areas

HB 1337 applies to GMA jurisdictions within urban growth areas (UGAs). The City of Spokane and Spokane Valley are inside the UGA, so the requirements apply there. For unincorporated Spokane County, the rules apply to the UGA portions of the county; outside the UGA, the county retains more discretion (RCW 36.70A.680(2)). This is why the county page treats UGA and non-UGA land separately.

The compliance timeline

HB 1337 has been in effect since July 23, 2023, and it preempts conflicting local rules where a jurisdiction has not yet adopted compliant regulations (RCW 36.70A.680(1)(a)). Full local adoption is tied to each jurisdiction's periodic comprehensive plan update under the GMA rather than one statewide calendar date, so the exact timing differs across the City of Spokane, Spokane County, and Spokane Valley and is still settling. Confirm whether your specific jurisdiction has adopted its update before relying on an older local rule.

What it means for your lot

If you read an older Spokane ADU document that lists a single-ADU-per-lot limit, an owner-occupancy requirement, or strict parking minimums, treat those as superseded by HB 1337 inside a UGA. Where an older local figure conflicts with the statute and the jurisdiction has not yet adopted a compliant rule, the statute controls. Check your jurisdiction page for the current local citation, then see whether you can build an ADU on your lot.

How the three Spokane jurisdictions have implemented it

State law sets the floor, but each city and county writes the local code a permit is reviewed against. Here is where each Spokane-area jurisdiction stands:

• City of Spokane: the city has adopted HB 1337 into its code. Two ADUs per lot, no general owner-occupancy requirement, and the current size, height, and setback standards are published with their SMC citations on our City of Spokane rules page.
• Unincorporated Spokane County: the HB 1337 baseline applies inside the urban growth area, and the county sets its own standards outside it. Our county rules page explains the split and where to confirm parcel specifics.
• Spokane Valley: the city's municipal code is still being updated to match state law, so the HB 1337 baseline controls where the older local code is stricter. Our Spokane Valley rules page covers the current baseline and what to confirm with the city.