How Federal Way Handles Accessory Structures: A Practical Guide

Federal Way maintains 125 local ordinances across all categories, and 5 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Federal Way falls on the strict-to-permissive spectrum compared to other cities.

Carport Rules

Carports in Federal Way are accessory structures under FWRC Title 19 and generally need permits if over 200 sq ft. Setbacks, height, and lot-coverage apply. Fabric carports in front yards are often restricted.

Key details: Permit Threshold: >200 sq ft. Detached Setback: Typ. 5 ft side/rear. Height: Typ. 12-15 ft. Code: FWRC 19.200. Front Yard Fabric: Often restricted.

Unpermitted carport over 200 sq ft: civil infraction under FWRC 1.15, retroactive permit, or removal. Front-yard temporary carport violations: civil infraction plus removal order.

Tiny Homes

Federal Way allows tiny homes on permanent foundations as ADUs or primary dwellings under FWRC 19.200 and 19.265. Tiny homes on wheels are RVs and cannot be permanent dwellings on residential lots.

Key details: Foundation Tiny Home: Allowed (ADU rules). Tiny Home on Wheels: Not as permanent home. Max ADU Size: 1,000 sq ft. State Code: IRC Appendix AQ. Code: FWRC 19.200 / 19.265.

Using a THOW as a permanent residence in a residential zone: civil infraction under FWRC 1.15 plus order to vacate. Building a non-compliant permanent tiny home: stop-work order and required remediation.

ADU Rules

Federal Way allows up to 2 ADUs per single-family lot under FWRC 19.200/19.265, updated for WA HB 1337 (2023). Max 1,000 sq ft each, attached or detached. Owner-occupancy is no longer required.

Key details: Max ADUs: 2 per single-family lot. Max Size: 1,000 sq ft. Owner Occupy: Not required (HB 1337). State Law: HB 1337 (2023). Code: FWRC 19.200 / 19.265.

Unpermitted ADU construction: stop-work order, civil infraction under FWRC 1.15, and required retroactive permit or removal. Short-term rental of ADUs may require STR registration.

The rules around adu rules in Federal Way lean permissive, but that does not mean anything goes.

Shed Rules

Federal Way exempts one-story sheds up to 200 sq ft from building permits under FWRC 13.15 and WAC 51-16-080. Larger sheds, electrical/plumbing work, or critical-area locations need permits. Zoning setbacks always apply.

Key details: No-Permit Size: Up to 200 sq ft. Setback: Typ. 5 ft side/rear (RS). Electric/Plumb: Permit required. Code: FWRC 13.15 + WAC 51-16-080. Permit Center: (253) 835-2607.

Shed built without required permit: stop-work order, civil infraction under FWRC 1.15, retroactive permit fees (typically 2x normal) or required removal. Setback violations may also trigger enforcement.

Federal Way is more permissive than most cities when it comes to shed rules. That said, there are still limits.

Garage Conversions

Garage conversions in Federal Way require building permits under FWRC 13.15 and 13.22. Habitable conversions trigger egress, insulation, smoke/CO, and utility permits. Conversions to ADUs are allowed under HB 1337.

Key details: Permit: Required. Code: FWRC 13.15 + 13.22. Egress Window: Required in bedrooms. ADU Option: Allowed (HB 1337). Parking Replace: May be required.

Unpermitted garage conversion: stop-work order plus civil infraction under FWRC 1.15. Retroactive permits typically require opening walls for inspection or full removal of the conversion. Habitable-space defects can create life-safety code violations.

The Bottom Line

Compared to many U.S. cities, Federal Way gives residents more room on accessory structures. 2 of the 5 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

All of the above reflects Federal Way's municipal code as of our last review. If you need specifics on fines, exemptions, or filing requirements, the detailed ordinance pages linked above have the full breakdown.