Accessory Structures in Harford County, MD (2026)
4 rules for unincorporated Harford County, Maryland.
Verified from official government sources
ADU Rules
Harford County allows one accessory dwelling unit (ADU) per lot in the AG, RR, R1-R4, RO and VR Districts under § 267-28B(8)(b) of the zoning code, so a relative can live within a family member's home. The ADU must be attached to or located inside the existing house, sized between 300 and 1,500 square feet, and capped at 2 bedrooms.
Harford County Accessory Dwelling Unit Rules
Some RestrictionsHarford County Code § 267-28B(8)(b)
One ADU is permitted on a single lot in the AG, RR, R1, R2, R3, R4, RO and VR Districts, provided that: ... The ADU shall be physically attached to or located within a single-family detached dwelling unit on the lot. ... The ADU shall be at least 300 square feet in size but shall not exceed the lesser of 1,500 square feet or 50% of the total habitable space of the existing single-family detache...
ADU Owner Occupancy
Harford County allows one accessory dwelling unit per lot in the AG, RR, R1-R4, RO and VR Districts, but only to house a relative, and the property owner must live in either the main house or the ADU as a legal permanent residence.
Harford County ADU Owner-Occupancy Rule
Some RestrictionsHarford County Code § 267-28B(8)(c)
(8) Accessory dwelling units (ADU). ... (a) Purpose. The purpose of the accessory dwelling unit is to allow a relative to live in an accessory dwelling unit within a family member's principal dwelling unit. (b) One ADU is permitted on a single lot in the AG, RR, R1, R2, R3, R4, RO and VR Districts, provided that: ... (c) The property owner shall occupy, as his or her legal permanent residence, ...
ADU Rental Restrictions
Harford County's accessory dwelling unit rule is not a general rental license: § 267-28B(8)(a) states its purpose is 'to allow a relative to live in an accessory dwelling unit within a family member's principal dwelling unit,' and § 267-28B(8)(c) requires the owner to occupy one of the two units as a legal permanent residence while a relative occupies the other.
Harford County ADU Rental Restrictions
Significant RestrictionsHarford County Code § 267-28B(8)(a), (c), (h)
Purpose. The purpose of the accessory dwelling unit is to allow a relative to live in an accessory dwelling unit within a family member's principal dwelling unit. ... The property owner shall occupy, as his or her legal permanent residence, either the principal single-family detached dwelling unit or the accessory dwelling unit, and the other dwelling unit shall be occupied by the relative. ......
Shed & Carport Rules
In unincorporated Harford County, a shed or detached garage counts as an accessory structure under § 267-27 of the zoning code and needs a zoning certificate before construction, per § 267-27B. On AG, RR, R1-R4 and VR lots it cannot exceed 50% of the house's square footage or 1,000 square feet, whichever is bigger, and must sit at least 3 feet off the side or rear lot line.
Harford County Shed and Accessory Building Rules
Some RestrictionsHarford County Code § 267-27B, C(1), C(6)(b)
All accessory uses and structures, whether or not specified in this section, require the issuance of a zoning certificate. ... In the AG, RR, R1, R2, R3, R4 and VR Districts, an accessory structure shall neither exceed 50% of the total square footage of the principal structure or 1,000 square feet, whichever is greater. The height of the accessory structure shall not exceed the height of the pr...
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