Seattle limits the percentage of a lot that can be covered by structures under SMC Title 23, with NR3 residential zones allowing up to 35 percent lot coverage for the principal structure plus additional allowances for accessory structures.
Lot coverage is the percentage of a lot area covered by structures at ground level. In NR3 zones, the maximum lot coverage for the principal structure is 35 percent, with total lot coverage including all structures capped at 45 percent (including accessory structures and ADUs). Certain elements are excluded from lot coverage calculations, including decks lower than 36 inches above grade, solar panels, fences, and the first 36 inches of roof overhangs. Lots smaller than 3,200 square feet may have modified coverage allowances. The 2025 NR zoning update adjusted some coverage limits to accommodate additional housing options like ADUs and DADUs. Commercial and multifamily zones generally allow higher lot coverage, with some downtown zones permitting up to 100 percent coverage. FAR (Floor Area Ratio) provides an additional bulk control separate from lot coverage.
Exceeding lot coverage limits without an approved variance is a code violation. SDCI reviews lot coverage during permit review and may require plan modifications. Post-construction violations discovered through complaints may require removal of encroaching structures.
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Side-by-side rule comparisons with other cities in King County.
See how other cities in King County handle lot coverage limits.
See how Seattle's lot coverage limits rules stack up against other locations.
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