Girdletree

Worcester County Zoning Section ZS 1-322 conditionally permits one accessory dwelling unit per lot in the A-1 Agricultural, A-2 Resource Conservation, E-1 Estate, R-1 Rural Residential, R-2 Suburban Residential, R-3 Multifamily Residential, and V Village zoning districts, in addition to one primary single-family detached dwelling. The ADU may be (a) attached/integrated into the primary dwelling, (b) a converted portion of a permitted accessory structure such as a garage or carriage house, or (c) detached. Owner-occupancy of either the primary or the accessory unit is required, with the Department of Review and Permitting (DRP) authorized to require an owner-occupancy affidavit at permit issuance and on resale. The accessory unit may not be subdivided or sold separately from the primary dwelling. Detached ADUs are capped at 900 square feet of gross floor area on parcels under 1 acre and at 1,000 square feet on parcels of 1 acre or more; the ADU footprint must observe the accessory-structure setbacks of the underlying district (typically 10 ft side, 15 ft rear in residential districts, and reduced setbacks in the Estate and Agricultural districts). One additional off-street parking space is required for the ADU beyond what the primary dwelling needs. Properties on private septic require Worcester County Environmental Programs sign-off that the existing or upgraded on-site sewage disposal system can support the added bedroom count under the Maryland Department of the Environment Bay Restoration Fund rules. In the Atlantic Coastal Bays Critical Area Overlay (Section ZS 1-116 et seq.), the ADU counts toward the per-acre density of the underlying Critical Area classification (IDA, LDA, or RCA), and detached ADUs in the RCA classification are limited to one per 20 acres absent a growth-allocation award. Worcester County is in the process of amending Section ZS 1-322 to align with the Maryland HB 1466 / SB 891 (Accessory Dwelling Units Act) statutory floor by the statewide 2026-10-01 deadline.

• Atlantic Coastal Bays Critical Area Overlay — A detached ADU on an RCA-classified parcel may be limited to one per 20 acres absent a growth-allocation award from the County Commissioners; LDA-classified parcels are capped at 15% lot coverage with offsets required for new impervious surface; IDA parcels face the most permissive density but still require buffer plantings and stormwater management. Worcester County, like the Chesapeake Bay counties, is required to maintain records of all Critical Area accessory-dwelling building permits and to report them periodically to the Critical Area Commission for review.
• Floodplain Management Overlay (Coastal Velocity Zones) — ADUs added to existing principal dwellings in the floodplain require elevation certificates. The substantial-improvement rule applies if the addition value exceeds 50% of the principal structure's pre-improvement assessed value, in which case the entire structure must be brought into compliance with the elevation standard - a frequent budget-buster on legacy slab-on-grade ocean-bay cottages.
• Forest Conservation Act — Pure interior ADUs rarely trigger FCA; new footprint, land clearing, or grading associated with a detached ADU on a wooded parcel may require Forest Conservation Plan compliance. Worcester is one of the Maryland counties where the Forest Conservation Act is enforced county-wide rather than only on subdivision applications.
• Assateague Island National Seashore Adjacency — Not strictly a zoning overlay - this is an inter-jurisdictional coordination layer that occasionally affects ADU site planning on bay-front parcels, particularly with respect to exterior lighting cutoff and septic-system nitrogen loading near park boundaries.