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All ADU Regulations

Renton, Washington

Renton is a perfect place to build an ADU. Here are Renton's up-to-date ADU rules.
Updated Jul 21, 2023


Renton is an industrial city located along the southeast shore of Lake Washington and Cedar River. Home to Boeing’s main assembly plant and several other industries, Renton features a rich history and hub for industrial operations. With a historic downtown and a variety of community events, coupled with the town’s proximity to major cities, Renton is an ideal place to work and live.


Most residential zones in Renton, including C, R-1, R-4, R-6, R-8, R-10, and R-14 zoned properties, are allowed to build ADUs.

Number of units

One ADU is allowed on a single-family dwelling lot if it meets underlying zoning requirements.

Building size

The size of an ADU depends on the lot size:
  • For lots less than 3000 square feet, the maximum size of an ADU is 600 square feet.
  • For lots greater than 3000 and less than 5000 square feet, the maximum size will be 700 square feet.
  • For lots greater than or equal to 5,000 and less than 7,000 square feet, the maximum size will be 800 square feet.
  • For lots greater than or equal to 7,000 and less than 9,000 square feet, the maximum size will be 900 square feet.
  • For lots greater than 9,000 square feet, the maximum ADU size is 1,000 square feet.


ADUs must be a minimum of 6 feet from the primary residence. They are not allowed between the primary structure and the street, unless approved by the Conditional Use Permit process. Rear yard setbacks in all zones are 5 feet, while minimum side yard setbacks vary by zone.


One additional parking space is required for ADUs in most cases. ADUs located within a ¼ mile of a mass transit facility are exempt from off-street parking requirements.


Either the primary dwelling unit or the ADU must be occupied by an owner of the property unless the applicant applies for and is granted a Conditional Use Permit.
Cottage is here to help you navigate the ADU process. Reach out to us and we’ll help you build a custom ADU to fit your unique property characteristics and local regulations!

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