All ADU Regulations

Sammamish, Washington

Sammamish is a perfect place to build an ADU. Here are Sammamish's up-to-date ADU rules.

Updated
July 21, 2023
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Sammamish

Sammamish is home to many families, residents, and wildlife with its proximity to Lake Sammamish, local greenery, and major metropolitan hubs. The suburban town, located right next to the beach and about 20 miles east of Seattle, offers a great deal of outdoor activities, scenic hikes, and thousands of acres of parks for residents and visitors to enjoy. With its short drive to metropolitan areas, Sammamish is an ideal place to live, work, and vacation within Washington!

Zoning

ADUs can be developed in Urban Residential zones (R-1, R-8, R-12, and R-18).

Number of units

One ADU is allowed per primary single detached dwelling unit.

Building Size

The maximum size of a ADU in Sammamish is 1,000 square feet when detached. When one of the dwelling units is contained within the existing residence, then the floor area will not exceed 40-50% of the floor area of the existing unit.

Setbacks & Height

  • R-1: Max height is 35 ft. The ADU will be placed at least 20 feet from the front property line, and 10 ft setbacks for rear/side yard.
  • R-4 & R-6: Max height is 35 ft. The ADU will be placed at least 15 feet from the front property line, 10 feet from rear property line, and 15 feet from side yard.
  • R-8: Max height is 35 ft. The ADU will be placed at least 10 feet from the front property line, and 10 ft setbacks for rear/side yard.
  • R-12 & R-18: Max height is 60 ft. The ADU will be placed at least 10 feet from the front property line, and 5 ft setbacks for rear/side yard.
  • Exceptions: Regardless of zoning district, if the property is on a major street, the minimum setback front yard is 30 feet. Rear and side yard setbacks can be reduced to 5 feet by having an agreement from the adjoining property owner, given that it is recorded with the King County’s Recorder Office.

Parking

No additional parking is required for an ADU.

Owner-occupancy

Either the principal dwelling unit or the accessory dwelling unit must be occupied by an owner of the property.

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!

Design and build with confidence.