Federal Way, WA Building Setbacks & Zoning: Lot Coverage Limits (2026)
Key Facts
- RS 35.0 / RS 15.0 max
- 50% lot coverage
- RS 9.6 / RS 7.2 / RS 5.0 max
- 60% lot coverage
- SE zone max
- 10% lot coverage
- Middle housing combo
- Coverage cap relaxed to 100%
- Calculation method
- FWRC 19.110.020, impervious surface / lot area
Summary
Federal Way caps impervious lot coverage, meaning every structure, driveway and other surface that blocks water percolation, at 50 percent of lot area in the RS 35.0 and RS 15.0 single-family zones and 60 percent in the RS 9.6, RS 7.2 and RS 5.0 zones under FWRC 19.200.010, calculated under the citywide method in FWRC 19.110.020.
(1) General. Except as specified in subsection (2) of this section, the area of all structures, pavement and any other impervious surface on the subject property will be calculated as a percentage of total lot area, exclusive of the area of any recorded access easements, in determining compliance with maximum lot coverage required in this title... 6. Maximum lot coverage is as follows: a. In RS 35.0 = 50%. b. In RS 15.0 = 50%. c. In RS 9.6 = 60%. d. In RS 7.2 = 60%. e. In RS 5.0 = 60%. ... g. When combined with middle housing on the same lot, the lot coverage maximum in all RS zones shall be 100%.
Official source re-checked September 8, 2026: no newer edition of the code had been published (publisher’s edition: current through Ordinance 26-1049, passed August 11, 2026).
Full Breakdown
020 sets the citywide method for calculating lot coverage: the area of every structure, area of pavement and any other impervious surface, meaning any surface that will not let water percolate into the soil below, is totaled and expressed as a percentage of the lot's total area, excluding any recorded access easement. Where a property has more than one use, the coverage limit for whichever use predominates governs the whole site. A carve-out applies to flag lots: the vehicular access easement, private tract, or driveway portion running through the "flag pole" or "access panhandle" of the lot is not counted toward the coverage limit.
The actual percentage varies by zone. 0, its smaller-lot subzones. 010, reflecting its five-acre minimum lot size and rural character. Where middle housing, such as duplexes, triplexes or cottage housing, is combined with a detached dwelling on the same RS-zoned lot, the coverage cap is relaxed to 100 percent of the lot, removing the usual limit entirely for that combination.
Violations & Fines
Covering a lot beyond its zone's maximum, whether with a house addition, a garage, a patio or added paving, violates FWRC 19.200.010 or FWRC 19.195.010 and is treated as a Title 19 zoning violation. The city issues a notice and order to correct under FWRC 1.15.040, and if the excess coverage is not removed or permitted by the correction date, a penalty accrues daily starting at $100 for a first violation and rising to $500 for repeated violations of the same kind.
Frequently Asked Questions
What counts toward lot coverage in Federal Way?
What is the maximum lot coverage for a Federal Way house?
Does adding an ADU change the lot coverage limit?
Sources & Official References
Other rules in Federal Way
Compare Federal Way to another location·View the Washington building setbacks & zoning overview
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Lot Coverage Limits in Nearby Cities
How other cities in King County handle lot coverage limits.