Royal Oak, MI Accessory Structures: Garage Conversions (2026)

Section 770-22A(11) of the Zoning Ordinance draws a line between a true accessory building, such as a detached garage or shed, and a structure that has effectively become a second dwelling. Under that subsection, an 'accessory building' does not include a structure that carries a combination of services, water, sewer, gas, electric, telephone and/or cable, that makes it easily convertible to habitable space, with the Zoning Administrator making that determination. A garage wired and plumbed like a small apartment therefore falls outside the accessory-building classification and instead has to be reviewed as a dwelling unit or an unpermitted second residence.

Once a structure is treated as a dwelling rather than an accessory building, § 770-23A's floor area minimums apply: in the One-Family Residential and One-Family Large Lot Residential Zones, a single-family dwelling unit's usable floor area cannot fall below the smallest adjacent single-family dwelling's floor area, and in no case can it be less than 1,000 square feet for a one-family dwelling or 1,300 square feet for a one-family large lot dwelling, based on City Assessor's office records. A converted garage's typical footprint, capped elsewhere in § 770-22A(5) at 800 square feet of ground floor area for all accessory buildings combined, will rarely reach that dwelling-unit minimum, which is part of why the City treats a habitable-space conversion as a zoning question rather than a simple remodel. An owner considering a garage conversion needs Zoning Administrator and Building Official sign-off before adding the utility combination that would trigger this section.