Renton, WA Accessory Structures: Shed & Carport Rules (2026)

RMC 4-2-110E governs detached accessory buildings citywide. In RC and R-1, owners may build two structures up to 720 square feet each, or one up to 1,000 square feet, plus a barn or stable up to 2,000 square feet on lots of 5 acres or more. R-4, R-6 and R-8 allow the same 720/1,000 square foot options without the barn exception. R-10 and R-14 instead limit accessory buildings to one per residential unit at 400 square feet (architecturally consistent with the principal structure), or 150 square feet for greenhouses, sheds and similar structures.

General accessory building height is capped at 12 feet in RC through R-14, and 25 feet in RMF/RMF-2, though it can never exceed the height of the primary dwelling for animal husbandry or agricultural structures. Detached accessory buildings must sit at least 4 feet from any residential structure or be reclassified as attached. Side yard setbacks are 5 feet in RC/R-1 and 3 feet in R-4 through RMF-2 (0 feet if sited between the rear of the house and the rear property line); rear yard setbacks are 5 feet in RC and 3 feet elsewhere, with the same rear-lot-line exception, and at least 25% of the rear yard's lineal length must stay unoccupied when a building sits within 10 feet of the rear property line.

Front and secondary front yard setbacks match the primary structure's setback, and accessory structures cannot be placed between the primary structure and the street. Total floor area of all accessory buildings cannot exceed the floor area of the primary residence, and combined lot coverage of the house plus accessory buildings cannot exceed the zone's maximum lot coverage.