ADU Regulations in Federal Way, Washington
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.
| Regulation | Requirement |
|---|---|
| Maximum Size | 1,000 sq ft |
| Property Setbacks | 5 ft rear, 5 ft side |
| Extra Parking Required | Required (1 space) |
| Owner Occupancy | Not required |
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
📥 Download the Complete Federal Way ADU Cheat Sheet
Get the step-by-step permit checklist, official government forms, direct planning department contacts, and estimated fees — all in one printable PDF for Federal Way, Washington.
Download the Complete Federal Way ADU Cheat Sheet — $12Frequently 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.
How big can my ADU be in Federal Way?
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 about setbacks and other requirements in Federal Way?
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. California state law (AB 68) limits local setback requirements to 4 feet for existing structures, but always verify with local zoning.
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