Alexandria, VA Accessory Structures: ADU Permits (2026)

Alexandria's Zoning for Housing/Housing for All initiative, adopted by City Council on November 28, 2023, was one of the most significant Virginia zoning reforms of the decade. The package amended Title 4 (Zoning Ordinance) of the Alexandria City Code to eliminate single-family-only zoning across the city and allow ADUs by right in nearly all residential districts (R-20, R-12, R-8, R-5, R-2-5, RA, RB, RC, RCX, RM, and others). A homeowner can build a detached backyard cottage, attached addition, or internal conversion (basement, attic, or interior unit) subject to size and setback limits. Typical limits under the post-2023 ordinance: maximum 500-800 sq ft or a percentage of the principal dwelling depending on lot size and district; setbacks generally matching accessory-structure rules (commonly 8 ft rear, 8 ft side for detached); height limited to the lesser of the principal dwelling height or accessory structure limits (typically 25-30 ft). The ADU shares the lot with an existing principal dwelling. Permits required: zoning compliance review through Planning and Zoning; building permit through Code Administration under the 2021 Virginia USBC (based on 2018 IRC with Virginia amendments); and trade permits for electrical, mechanical, and plumbing. Filing is through Alexandria's online permit center (Eden / APEX system). Old and Historic Alexandria District (most of Old Town south of First Street and east of West Street) and the Parker-Gray Historic District require Board of Architectural Review (BAR) Certificate of Appropriateness before zoning permit issuance. Resource Protection Area buffers (100 ft from the Potomac, Cameron Run, Holmes Run, Four Mile Run, and Hooffs Run) under the Chesapeake Bay Preservation Act restrict ADU placement on many waterfront and tributary-adjacent lots. FEMA flood zone construction (Old Town waterfront and Eisenhower Valley A and AE zones) requires elevation per the Virginia USBC flood provisions.