Accessory Structures in Federal Way, WA

Federal Way maintains 124 local ordinances across all categories, and 3 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.

ADU Impact Fees

Federal Way caps both transportation and park impact fees for accessory dwelling units at 50 percent of what a detached single-family home pays. The discount applies automatically when the city assesses fees at building permit issuance under FWRC 19.91.060 and 19.92.060.

Key details: Transportation fee cap: 50% of a detached SFD fee. Park impact fee cap: 50% of a detached SFD fee. Transportation citation: FWRC 19.91.060(6). Park fee citation: FWRC 19.92.060(5). Payment due: Before building permit issuance.

The community development department withholds the building permit until the impact fees are paid or a lien is recorded against the property under FWRC 19.100.075(3); occupancy is likewise blocked where no permit is required but the fee remains unpaid. Determinations on independent fee calculations or fee amounts can be appealed under FWRC 19.91.180 for transportation fees and FWRC 19.92.150(4) for park fees.

Shed & Carport Rules

A storage shed in a required side or rear yard needs discretionary Process III approval in Federal Way, capped at eight feet high, 120 square feet, and a 10-foot facade, under FWRC 19.125.160(9). Front yards are off-limits entirely.

Key details: Approval required: Process III, side/rear yards only. Front yard sheds: Not allowed under this provision. Max height: 8 feet above finished grade. Max floor area: 120 square feet. Max facade length: 10 feet parallel to property line.

Placing a storage shed in a required yard, especially a front yard, without the required Process III approval, or exceeding the eight-foot height, 120-square-foot area, or 10-foot facade limits, is a code violation enforceable as a civil infraction under Chapter 1.15 FWRC. FWRC 1.15.110 sets the default penalty at $100 for a first violation, $200 for a second violation of the same nature, and $300 for a third or continuing violation, plus any costs of bringing the structure into compliance or removing it.

This is one of the stricter rules in Federal Way's municipal code. If you are unsure whether your situation complies, it is worth checking with the city before proceeding.

ADU Rules

Federal Way allows up to two accessory dwelling units per single-family lot under FWRC 19.200.180, each capped at 1,000 square feet and two bedrooms unless the ADU is attached and built inside the existing home's footprint. One parking space per unit is required, dropping to zero within a half mile of a major transit stop.

Key details: Max ADUs per lot: 2, plus the primary dwelling. Max ADU size: 1,000 sq. ft. living area. Max bedrooms: 2 per ADU. Parking: 1 space per ADU, 0 near transit. Review process: None required for the ADU use.

Building or occupying an ADU that exceeds the 1,000-square-foot cap, adds a third bedroom, or skips the required parking violates FWRC 19.200.180 and is enforced as a Title 19 zoning violation under FWRC 1.15.040: a notice and order to correct, then an accruing daily penalty of $100 for a first violation up to $500 for repeated or continuing violations of the same kind.

The Bottom Line

Federal Way's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Federal Way is broadly strict or permissive.

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.