Gaithersburg, MD Accessory Structures: Garage Conversions (2026)

Gaithersburg allows garage conversions to living space with proper permits and zoning compliance. A building permit is required from the Building Division at (301) 258-6330. The converted space must meet International Residential Code standards for habitable rooms, including minimum ceiling height of 7 feet, natural light and ventilation (window area at least 8 percent of floor area), adequate insulation to meet current energy code, and egress windows in sleeping rooms. The existing garage slab may need moisture barrier improvements. Electrical, plumbing, and HVAC work each require separate trade permits. The conversion must not reduce the property's required off-street parking spaces below the minimum for the zoning district. In most single-family zones, two off-street parking spaces are required. If converting a two-car garage, alternative parking solutions such as driveway expansion may be needed. Converting a garage to an accessory dwelling unit follows Gaithersburg's ADU regulations including owner-occupancy and size limits. The exterior appearance after conversion must be compatible with the neighborhood character. Contact the Department of Planning and Code Administration for a pre-application meeting to discuss feasibility.