Renton, WA Accessory Structures: Garage Conversions (2026)

Converting a garage to livable space in Renton requires a building permit under RMC 4-5-060 and the Washington State Residential Code. The converted space must meet all habitable room requirements: minimum ceiling height of 7 feet, emergency egress windows in sleeping rooms (5.7 square feet net opening for second story, 5.0 for grade level), natural light and ventilation (or mechanical ventilation meeting code), insulation meeting WA Energy Code, smoke and CO alarms, and proper heating. Plumbing and electrical upgrades require separate permits. If the conversion creates an independent dwelling unit with its own kitchen, it becomes an ADU and must meet RMC 4-2-115 ADU standards — conveniently, converting an attached garage to an ADU is one of the most cost-effective ADU strategies under HB 1337. Parking replacement has changed: the city previously required replacement covered parking when a garage was converted, but the current rule is that no off-street parking is required within one-half mile of major transit stops, and otherwise one space is typical. Exterior changes like filling in the garage door must match primary dwelling design under Renton's residential design standards. Structural review is often needed if the garage door header is load bearing.