Renton, WA Building Setbacks & Zoning: Lot Coverage Limits (2026)

Renton Municipal Code 4-2 sets lot coverage and impervious surface limits by zoning district. In R-4 and R-6 zones, maximum building coverage is typically 40 to 50 percent, and R-8 allows up to 50 percent coverage by the primary and accessory structures combined. R-10 and R-14 higher density zones allow greater coverage. Total impervious surface, which includes driveways, patios, and pool decks in addition to buildings, is separately capped and triggers stormwater review under the Surface Water Design Manual when thresholds are exceeded. These limits protect the Cedar River, Black River, and Lake Washington from stormwater pollution and flooding. Lots within critical areas have reduced coverage allowances due to buffer and setback requirements. The Shoreline Master Program adds its own standards near Lake Washington. New or expanded impervious surfaces over 2,000 square feet typically require stormwater mitigation including infiltration or detention facilities. Coverage is calculated based on total lot area minus any easements that reduce buildable area. Confirm zone-specific limits and impervious caps with CED before designing.