Federal Way ADU Zoning Rules & Permit Guide

ADU Regulations in Federal Way, Washington

Updated September 29, 2026

Situated in King County between Seattle and Tacoma, Federal Way permits ADUs under Washington's HB 1337 framework. The city's location along the I-5 corridor makes it an attractive market for ADU development.

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

Additional Local Requirements for Federal Way

• ADU by right in residential zones
• Minimum 200 sq ft
• Short-term rental prohibited
• State law HB 1337 applies

Frequently Asked Questions About ADUs in Federal Way

Can I build an ADU in Federal Way?

Federal Way permits ADUs under Washington state law. Owner occupancy is not required.

What is the maximum ADU size allowed in Federal Way?

ADUs in Federal Way 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 Federal Way planning department before designing your project.

What are the setback requirements for an ADU in Federal Way?

ADUs in Federal Way 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 Federal Way's own land use code — confirm them with the city before you design.