Auburn, WA Zoning Overlays & Bonuses: Density Bonus Law (2026)

Auburn City Code 18.02.067(G) lets real property owned or controlled by a religious organization add housing at a 50 percent density bonus when building single-family residences or apartment buildings, but only if 100 percent of the resulting units are dedicated as affordable housing for households at or below the low-income threshold defined in RCW 35A.63.300(6)(b). That affordability commitment must run for at least 50 years, secured by a recorded covenant or deed restriction, and it survives even if the religious organization later sells the property. The organization must still pay all standard permit fees and mitigation costs, and the project has to meet the underlying zone's development standards; existing affordable housing rehabilitated by a religious organization under RCW 35A.63.300(6)(a) also qualifies.

Subsection (H) provides a separate 50 percent density bonus for existing commercial, mixed-use, and residential buildings that add dwelling units entirely within the existing building envelope, without cutting existing parking. It applies only in the RC, R-1, R-2, R-3, R-4, R-NM, R-F, C-2, C-AG, and M-1 zones, and only to buildings that received a final certificate of occupancy at least three years before the conversion permit application. Qualifying conversions are exempted from new parking requirements, from meeting the current energy code in unchanged conditioned space, from a transportation concurrency study under RCW 36.70A.070, and from SEPA environmental review under Chapter 43.21C RCW when the addition is confined to the existing building. Newly created space is not off the hook entirely: if the new dwelling square footage exceeds 2,500 square feet or 50 percent of the building's total square footage, the owner must document that projected energy use intensity meets the clean buildings performance standard in RCW 19.27A.210. Both bonus tracks are administered through the community development department's standard permit review and must be layered on top of the base and bonus unit calculations already set under ACC 18.02.065(C) and 18.25 ACC.