Kirkland, WA Accessory Structures: Garage Conversions (2026)

Kirkland allows up to two accessory dwelling units per single-family lot, and KZC 115.07(6) specifically exempts the conversion of an existing structure, including a detached garage, from the setback and lot coverage standards that would otherwise apply. The only condition is that the conversion can't increase any existing nonconformity beyond what already exists. Outside that exemption, ADUs generally must meet the same setbacks, height limits and lot coverage as a single-family dwelling in the zone.

The converted unit is capped at 1,200 square feet of gross floor area (KZC 115.07(4)), a figure that excludes attic space with less than five feet of ceiling height, uncovered rooftop decks and patios, and up to 200 square feet of covered or uncovered exterior features. Occupancy limits track the KMC Property Maintenance Code, and the unit may be sold separately from the primary house (subsection 2, Ownership). Habitable space converted from a garage still has to meet current building, fire, health and safety codes, though space that was legally built as habitable is grandfathered on ceiling height under subsection (8).

To convert a garage, the property owner applies for an ADU permit through the Planning and Building Department with a signed affidavit; if the work doesn't need a building permit, a registration form is filed instead. That registration requires a covenant recorded with the King County Recorder's Office disclosing the ADU, which stays on the property as long as the unit exists (subsection 9). Parking is often waived: no off-street space is required within a half-mile of a major transit stop. Decisions of the Planning Official are appealable under Chapter 145 KZC.