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

RMC 4-2-110A's residential development standards table sets maximum building coverage, including both primary and accessory structures, at 10% in the RC zone, 20% in R-1, 35% in R-4, 40% in R-6 and 50% in R-8. Maximum impervious surface area, which counts driveways, patios and other hardscape along with the building footprint, is set higher in every zone: 15% in RC, 25% in R-1, 50% in R-4, 55% in R-6 and 65% in R-8. RMC 4-2-110B extends the pattern into the higher-density residential zones: building coverage runs 55% in R-10 and 65% in R-14, with townhouses in R-14 allowed 70% and other attached dwellings limited to 35% (a 45% coverage cap is available for other attached dwellings through Hearing Examiner site development plan review).

Impervious surface caps in those zones reach 70% in R-10, 80% in R-14, and 75% for RMF-zone development. RMC 4-2-110E, which governs detached accessory buildings, ties back into this same limit: the lot coverage of the primary residential structure combined with all accessory buildings on a lot may not exceed the maximum lot coverage figure set for that zoning district, so a homeowner adding a shed or detached garage has to check the combined footprint against the applicable RC-through-R-14 percentage, not just the accessory structure's own footprint.