Seattle, WA Building Setbacks & Zoning: Lot Coverage Limits (2026)
Key Facts
- Base lot coverage cap
- 50 percent of lot in NR zones
- Stacked-unit bonus
- 60 percent for lots with stacked dwellings
- Transit-area bonus
- 60 percent for courtyard developments near frequent transit
- Minimum guaranteed coverage
- 625 square feet on constrained lots
- Governing section
- SMC 23.44.080
Summary
SMC 23.44.080 caps structure coverage at 50 percent of the lot in Seattle's Neighborhood Residential zones, rising to 60 percent for stacked dwelling units or for low-rise courtyard developments in frequent transit areas. Underground structures, small architectural projections, and low decks and porches don't count toward the cap.
A.Except as otherwise provided in this Section 23.44.080, the maximum lot coverage allowed for structures is 50 percent.B.The following areas shall not be counted in calculating the lot size for the purpose of calculating lot coverage in this Section 23.44.080:1.Riparian corridors;2.Wetlands and their buffers;3.Submerged lands and areas within the shoreline setback; and4.Designated non-disturbance area in steep slopes.C.Structures not counted. The following structures and portions of structures are not counted in lot coverage calculations:1.Underground structures;2.The first 36 inches of architectural features such as cornices, eaves, gutters, roofs, fireplaces, chimneys, and other similar features that project from principal and accessory structures;3.Decks or parts of a deck that are 36 inches or less above existing grade;... G.The maximum lot coverage allowed on lots with stacked dwelling units is 60 percent.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Municipal Code: Supplement 44 Update 1).
Full Breakdown
080(A) sets the general maximum lot coverage for structures in Neighborhood Residential zones at 50 percent of the lot. Subsection B excludes riparian corridors, wetlands and their buffers, submerged lands within the shoreline setback, and designated non-disturbance steep-slope areas from the lot-size calculation used to figure that percentage. H standards; and the floor area of Type A accessible dwelling units in buildings with up to ten stacked units. 09. Two bonuses raise the cap above 50 percent: subsection F allows 60 percent coverage within a frequent transit service area for courtyard-style developments under three stories arranged around a shared ground-level amenity area equal to at least 20 percent of the lot, and subsection G sets a flat 60 percent maximum for any lot with stacked dwelling units.
Violations & Fines
Building beyond the 50 percent lot coverage cap, or the 60 percent bonus threshold where it applies, without qualifying for one of the Section 23.44.080(C) exclusions is a zoning violation that SDCI will catch at permit review, requiring the applicant to redesign, remove excluded square footage, or seek Director relief under Chapter 25.09 before a permit issues.
Frequently Asked Questions
What percentage of my lot can I build on in Seattle?
Do decks and porches count toward lot coverage?
What if my lot has wetlands or a steep slope?
Sources & Official References
Other rules in Seattle
Compare Seattle 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.