House Bill 1337 - ADUs

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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, 2025Future - Effective starting July 1, 2025
Owner Occupancy*RequiredNot 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.
ADUMaximum 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.
FeesThe 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.

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, 2025Future - Effective starting July 1, 2025
Owner Occupancy*RequiredNot 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.
ADUMaximum 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.
FeesThe 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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  • Share I am planning to build an ADU per new state regulations as of 7/1/2025. Has the City of Renton developed any guidelines/code for what can be built. e.g. can it be build larger then my existing house at 1414 N. 32nd? Does it have to have the same appearance as my existing home? What will be the minimum set backs to property lines and other structures? Provide any details that you can at this point in time. Thank you, Mark Yormark on Facebook Share I am planning to build an ADU per new state regulations as of 7/1/2025. Has the City of Renton developed any guidelines/code for what can be built. e.g. can it be build larger then my existing house at 1414 N. 32nd? Does it have to have the same appearance as my existing home? What will be the minimum set backs to property lines and other structures? Provide any details that you can at this point in time. Thank you, Mark Yormark on Twitter Share I am planning to build an ADU per new state regulations as of 7/1/2025. Has the City of Renton developed any guidelines/code for what can be built. e.g. can it be build larger then my existing house at 1414 N. 32nd? Does it have to have the same appearance as my existing home? What will be the minimum set backs to property lines and other structures? Provide any details that you can at this point in time. Thank you, Mark Yormark on Linkedin Email I am planning to build an ADU per new state regulations as of 7/1/2025. Has the City of Renton developed any guidelines/code for what can be built. e.g. can it be build larger then my existing house at 1414 N. 32nd? Does it have to have the same appearance as my existing home? What will be the minimum set backs to property lines and other structures? Provide any details that you can at this point in time. Thank you, Mark Yormark link

    I am planning to build an ADU per new state regulations as of 7/1/2025. Has the City of Renton developed any guidelines/code for what can be built. e.g. can it be build larger then my existing house at 1414 N. 32nd? Does it have to have the same appearance as my existing home? What will be the minimum set backs to property lines and other structures? Provide any details that you can at this point in time. Thank you, Mark Yormark

    markyormark asked 3 months ago

    Hi, Mark –

    Thank you for your inquiry! 

    Staff continues working on drafting the required amendments for compliance with the state mandates, so nothing concrete to share for now. However, we are not proposing to increase maximum ADU size from 1,000 sq. ft., so you would not be allowed to construct an ADU that is larger than the existing residence. Feasibility and ADU size will depend upon ability to meet development standards (e.g., setbacks, impervious surface coverage, height, etc.). Existing standards can be found in RMC 4-2-110A, RMC 4-2-110C, and RMC 4-2-116.

  • Share Are adu sq ft floor space increasing on July 1st in rural King County on Facebook Share Are adu sq ft floor space increasing on July 1st in rural King County on Twitter Share Are adu sq ft floor space increasing on July 1st in rural King County on Linkedin Email Are adu sq ft floor space increasing on July 1st in rural King County link

    Are adu sq ft floor space increasing on July 1st in rural King County

    Rick asked 7 days ago

    The City of Renton is not increasing maximum building area for ADUs and the maximum ADU size will continue to be 1,000 sq. ft. However, all permitting and land use questions will need to go through King County. See the following contact information and question form for the King County Permitting Division:

    Department of Local Services, Permitting Division
    919 SW Grady Way, Suite 300
    Renton, WA  98057

    Ask them a question Fill out their form to get a response

    Customer service: call 206-296-6600 during the following hours: 9-11 a.m. and 12:30-2:30 p.m., Monday, Tuesday, Thursday, Friday.

Page last updated: 07 Mar 2025, 04:42 PM