Allegany County, MD Accessory Structures: ADU Rules (2026)

Land Development Services administers ADUs under Allegany County Code § 360-87, which permits accessory dwelling units in the B-1 (Neighborhood Commercial), B-2 (Major Commercial) and I (Industrial) Districts, subject to the general regulations of § 360-129. Section 360-129.C frames these as "dwelling units as accessory uses" attached to a commercial or industrial building: the new unit must be clearly subordinate in size to the primary commercial or industrial use it accompanies, and the same person must own both the dwelling unit and the associated business use, foreclosing a landlord adding an ADU to lease independently.

Because the R-1, R-2, GU, A and C Districts are not listed in § 360-87, a homeowner in one of the county's residential or agricultural zones cannot add a garage apartment or in-law suite as an accessory dwelling unit under this section; any such second unit would instead have to qualify separately, for example as a duplex conversion under § 360-83, which is itself restricted to certain districts and requires Board of Appeals approval as a special exception outside the R-2/GU Districts. A zoning permit application for a § 360-87 accessory dwelling unit goes through Land Development Services' standard permit procedure under Article XIV, with plan review and applicable fees set under § 360-72.