How Renton Handles Accessory Structures: A Practical Guide

Renton maintains 136 local ordinances across all categories, and 2 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Renton falls on the strict-to-permissive spectrum compared to other cities.

Shed & Carport Rules

Renton limits detached accessory buildings like sheds and garages to two structures of 720 square feet each (or one at 1,000 square feet) in most residential zones, capped at 12 feet tall, set at least 4 feet from the house, and no closer than 3 to 5 feet to side and rear property lines.

Key details: Max size, RC/R-1/R-4/R-6/R-8: 720 sq. ft. (x2) or 1,000 sq. ft. (x1). Max size, R-10/R-14: 400 sq. ft. (150 sq. ft. shed exception). Height limit (general): 12 ft.. Distance from house before reclassified attached: 4 ft.. Side yard setback: 5 ft. (RC/R-1); 3 ft. elsewhere.

Building a shed or accessory structure that exceeds the size or height cap, or that violates the setback or lot-coverage limits, is a zoning violation subject to Renton code compliance action, which can require the structure be resized, relocated or removed and can carry civil penalties accruing daily until the property is brought into compliance.

ADU Rules

Renton allows up to two ADUs per legal lot in the RC, R-1, R-4, R-6, R-8, R-10 and R-14 zones, attached or detached. Each ADU is capped at 1,000 square feet of gross floor area, with detached units held to 24 feet in building height and specific side and rear setbacks by zone.

Key details: Max ADUs per lot: 2 (attached and/or detached). Max floor area per ADU: 1,000 sq. ft.. Detached ADU height limit: 24 ft. to ridge/flat roof. Detached ADU side setback: 25 ft. (RC/R-1) to 4 ft. (R-10/R-14). Parking requirement: 1 space/unit, waived near transit.

Building without the required permits, or exceeding the 1,000 sq. ft. floor area cap, the 24-foot detached height limit, or the zone's setback minimums, is a zoning code violation enforced by Renton's Community and Economic Development Department under RMC Title I's general penalty and code compliance provisions, which can require correction and impose civil penalties per day of noncompliance until the unit is brought into conformance or removed.

The Bottom Line

Renton's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Renton is broadly strict or permissive.

Keep in mind that Renton can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.