Portsmouth, VA Accessory Structures: ADU Rules (2026)

Sec. 2-215 defines an ACCESSORY DWELLING UNIT (ADU) as "a secondary dwelling unit established in conjunction with and clearly subordinate to a principal dwelling unit," whether built into the same structure or as a detached building on the same lot. 2-216 permits ADUs by right in the Neighborhood Residential (NR), General Residential (GR), Urban Residential (UR), Urban Residential-Mixed (UR-M), Neighborhood Mixed-Use (NMU), Downtown D1-T3, and the Historic Residential (HR), Historic Limited Office (HLO), and Historic Limited Business (HLB) districts. The use-specific standards at Sec. 2-217(I)(3)(b) restrict ADUs to lots with a single-family detached dwelling; they are not permitted on multi-family, townhouse, two-family, or three- to four-family lots.

Only one ADU is allowed per lot, and it may be located inside the principal structure, physically attached with an operative interconnecting door, or built as a detached structure. A detached ADU must be separated from the principal structure as required by the Building Code and stay in the same zoning district as the principal home. The unit must have a minimum gross floor area of 300 square feet and cannot exceed 25 percent of the principal structure's floor area. Owners must provide one to two off-street parking spaces for the ADU, on top of the parking required for the main house, and manufactured homes, travel trailers, or campers cannot serve as an ADU unless state law under Va. Code Sec. 2-2290 allows it. Finally, an ADU can never be sold separately from the principal dwelling; it stays tied to the same deed.