Grant County, WA Accessory Structures: Garage Conversions (2026)

020(c)(9), titled 'Conversions,' specifically addresses turning an existing structure such as a detached garage into an ADU rather than building a new one from scratch. 020(c)(6). The provision then carves out one specific exception: if the existing garage is already nonconforming with respect to setbacks or lot coverage, the county does not require the owner to bring the structure into conformance before converting it, and the resulting ADU is allowed to retain that nonconformity rather than being forced to relocate or rebuild the garage's footprint.

That is a meaningful concession because many older detached garages in the unincorporated county predate current setback standards and would otherwise be barred from any expanded use. Everything else about the conversion is treated like any other ADU: it must be occupied as a permanent residence and cannot be used as a short-term rental under 30 consecutive days, and factory-built structures such as manufactured homes or tiny homes are not implicated by a garage conversion since the garage itself is the existing building being repurposed.