House Bill 1337 - ADUs
The Washington State legislature adopted new rules and regulations for Accessory Dwelling Units (ADUs) to expand housing opportunities.
An ADU is a dwelling unit on the same lot as a single-family, duplex, triplex, townhome, or other housing unit. It is a typical residential home with a kitchen, bedroom(s), and bathroom(s).
Cities across the state, including Renton, are required to update their local ADU regulations to comply with House Bill (HB) 1337 by June 30, 2025. See the table below for a summary of the current and future ADU requirements.
| Current- Effective through June 30, 2025 | Future - Effective starting July 1, 2025 | |
| Owner Occupancy* | Required | Not required. |
| Permissibility* | One detached ADU per residential lot is allowed. ADUs allowed as an accessory use to a detached single-family dwelling, a religious institution or social service organization, and must be consistent with the architectural character of the primary residential structure. | Two (2) allowed ADUs per residential lot when all development regulations are met – units may be attached or detached. ADUs may also be allowed as accessory uses to duplexes, triplexes, townhomes, and other housing units on a lot. No proposed changes to ADU regulations when accessory to religious institutions and social service organizations. |
| Parking | One required parking space. | Parking requirements based on distance to major transit stops and lot size. |
| ADU | Maximum ADU size is determined by lot size and principal size. | Local government may not limit maximum ADU size to less than 1,000 sq. ft. |
| Separate Sale* | Sale of ADUs as separate units not allowed. | Sale of ADUs as separate units is allowed. |
| Fees | The fees waivers and reductions available for impact fees, plan review, system development charges, and City of Renton utility hook-up fees end on January 1, 2025. | Impact fees will be charged at the rate of 50% of the principal unit. Plan review fees waived for PRADUs. |
*The restrictions placed on ADUs built before June 30, 2025, will no longer be in effect when the new legislation is adopted.
The city's Planning Commission will present and review proposed and required code adjustments. Renton residents are welcome to participate in public feedback.
In addition to code changes, the current ADU fee waivers will expire on December 31, 2024. New fee rates will go into effect on January 1, 2025, and July 1, 2025.
ADU architectural plans will continue to be offered through the city’s Permit Ready ADU Program for properties within Renton city limits. Please use the address locator and jurisdiction finder or contact Planning Customer Service to verify eligibility.
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