Sammamish ADU Zoning Rules & Permit Guide

ADU Regulations in Sammamish, Washington

Updated September 29, 2026

In eastern King County, Sammamish allows ADUs under Washington's HB 1337 framework. The city's affluent lakeside neighborhoods apply design review standards to new accessory units.

Below is a summary of the key zoning rules applicable to Accessory Dwelling Units in Sammamish as of 2026. Regulations are governed by Washington's HB 1337 (2023) which limits local ADU restrictions statewide.

Additional Local Requirements for Sammamish

• ADU by right in residential zones
• Minimum 200 sq ft
• WA HB 1337 limits local restrictions

Frequently Asked Questions About ADUs in Sammamish

Can I build an ADU in Sammamish?

This Washington city follows HB 1337 which limits local ADU restrictions. Parking may be waived near transit.

What is the maximum ADU size allowed in Sammamish?

ADUs in Sammamish can be up to 1,000 square feet, subject to the property's zoning and lot coverage limits. Always confirm the exact allowed size with the Sammamish planning department before designing your project.

What are the setback requirements for an ADU in Sammamish?

ADUs in Sammamish generally require setbacks of 5 ft rear, 5 ft side. Washington's HB 1337 (2023) limits how restrictive local ADU rules can be, but the exact setback figures come from Sammamish's own land use code — confirm them with the city before you design.