Gore

Frederick County, Virginia regulates accessory dwelling units through its Zoning Ordinance, codified as Chapter 165 of the Frederick County Code, administered by the Department of Planning and Development and adopted by the Frederick County Board of Supervisors. Virginia is a Dillon Rule state and has NOT enacted a statewide ADU preemption law — the state zoning-enabling statutes at Va. Code § 15.2-2280 et seq. delegate zoning authority entirely to localities — so every ADU rule that applies to a Frederick County parcel is local. Frederick County's zoning ordinance permits 'accessory apartments' and 'garage apartments' (terms used in the county code that substantially overlap with the ADU concept) as accessory uses subject to zoning-district conditions, lot-area minimums, owner-occupancy of the principal dwelling, and a conditional-use-permit (CUP) process in some districts. The RA (Rural Areas) district — which covers the majority of the county's unincorporated land area surrounding the independent city of Winchester — permits accessory apartments with specific size and occupancy limitations; the RP (Residential Performance) and R5 (Residential Recreational Community) districts impose tighter conditions. Frederick County is among the Virginia counties that have considered but not enacted by-right ADU allowance during the 2022-2025 General Assembly cycle when statewide ADU bills were pending; accessory-apartment approval in Frederick County remains a locally-administered process without a statewide ministerial-review floor.

• Frederick County Code Chapter 165 (Zoning Ordinance) — Accessory apartments and garage apartments
• Frederick County Code Chapter 165, Article IV — Supplementary Use Regulations
• Frederick County Comprehensive Plan 2040 — Housing element
• Virginia Code § 15.2-2280 et seq. — State zoning enabling authority

State-floor overlay: None. Virginia has not enacted a statewide ADU preemption law. Va. Code § 15.2-2280 et seq. delegates zoning authority to localities without imposing a floor on ADU permissibility, ministerial approval, minimum size, or parking. Frederick County's Chapter 165 is therefore the operative rule set for every ADU question — allowance by district, size limits, owner-occupancy, parking, permit process, and fees are all locally set. ADU bills introduced in the 2022-2025 General Assembly sessions (seeking by-right allowance, ministerial review, and parking preemption) did not advance; the 2026 session had not closed the gap as of 2026-04-21.

Frederick County, Virginia administers or cooperates in several overlay and environmental-review regimes that can affect ADU siting on unincorporated parcels: (1) the Chesapeake Bay Preservation Area program under the Virginia Chesapeake Bay Preservation Act — Frederick County lies in the Potomac River drainage and falls within the statutory Tidewater-Virginia Chesapeake Bay Preservation Area reach only in its eastern portions; however, statewide erosion-and-sediment-control rules apply generally; (2) FEMA Special Flood Hazard Areas along the county's principal watercourses — Opequon Creek, Back Creek, Cedar Creek, and tributaries of the Shenandoah River and Potomac River — subject to the county's floodplain-management ordinance; (3) historic overlay districts administered by the county's Historic Resources Advisory Board (HRAB), protecting rural-historic districts and individual landmark properties associated with the county's Shenandoah Valley and Civil War heritage; (4) karst / sinkhole geology review — Frederick County sits on carbonate bedrock in a karst-prone region of the northern Shenandoah Valley, so site-specific geotechnical review for foundation and septic design is commonly required on parcels with known sinkholes or karst features; (5) wildfire-risk considerations — while Virginia does not maintain Very-High-Fire-Hazard Severity Zones comparable to California's VHFHSZ, the Virginia Department of Forestry maintains Firewise USA program participation in some Shenandoah-Valley communities and applies the International Wildland-Urban Interface Code standards to forest-interface properties. Airport Land Use Compatibility planning is administered around Winchester Regional Airport (operated by the Winchester Regional Airport Authority), whose airport influence area extends into portions of Frederick County.

• FEMA Special Flood Hazard Areas / Frederick County Floodplain Management Ordinance — Frederick County's Chapter 165 floodplain-district article enforces FEMA NFIP minimum floodplain-management standards. Applicants should confirm effective FIRM panel numbers and BFEs at design time. FEMA is conducting ongoing FIRM updates in the Potomac drainage; owners should verify current effective panels before design commitments.
• Frederick County Historic Resources Advisory Board (HRAB) — Historic overlay and advisory review — Historic-overlay review does not typically prohibit an ADU outright but may add design-review requirements (materials, scale, siting) for construction on or adjacent to designated historic resources. Non-overlay parcels are unaffected. The Cedar Creek and Belle Grove NHP is a federal / state partnership and does not by itself create local regulatory authority over private-parcel construction outside the park boundary.
• Karst / sinkhole geotechnical review (carbonate-bedrock region) — Karst review is not a formal 'overlay' in the zoning-ordinance sense — it is a set of engineering and health-department constraints applied parcel-by-parcel. An ADU that requires a new or expanded septic drainfield on a karst-affected parcel is the category most likely to face a substantive review, including geotechnical investigation, hydrogeologic evaluation, and alternative septic-system design (sand-mound, drip-irrigation, or advanced treatment systems approved by VDH).
• Winchester Regional Airport — Airport Influence Area / land-use compatibility — An ADU proposed within the airport's influence area may need to comply with avigation-easement disclosure requirements and Part 77 height-limit considerations; meaningful noise-contour impact is generally limited to the immediate runway environs for a general-aviation airport of Winchester Regional's scale. The airport authority does not exercise direct land-use approval authority on private parcels outside airport property; its influence is through county-referred review during site-plan or CUP processes.
• Virginia Department of Forestry / Wildland-Urban Interface — There is no Frederick County-specific WUI ordinance comparable to western-state WUI regimes. Construction standards for ADUs on forest-interface parcels follow the general Virginia USBC; voluntary Firewise USA measures (defensible space, ignition-resistant materials, roof and vent design) are encouraged but not mandated by county zoning.

Frederick County, Virginia's Department of Planning and Development (zoning, site-plan review, and land-use approvals) and Department of Inspections (building-permit, plan review, and inspection services) jointly administer ADU / accessory-apartment permitting for parcels in the unincorporated county. In Virginia's unusual geography, the independent city of Winchester is a separate jurisdiction that sits geographically surrounded by Frederick County but is not governed by the county — Winchester has its own planning, zoning, and building permit authorities. Frederick County permitting therefore applies to the unincorporated balance of the county (which is the vast majority of the county's roughly 414 square miles of land area) and to the town of Stephens City in the southeast corner. The county's permitting path for an accessory apartment is a sequenced process: (a) zoning determination by Planning and Development confirming the parcel's district and the district's accessory-apartment allowance; (b) conditional-use-permit application heard by the Planning Commission and decided by the Board of Supervisors when required by the zoning district; (c) building-permit application to the Department of Inspections; (d) health-department approval for on-site septic and well where applicable (most of Frederick County's rural-areas parcels are on private well and septic, not public utilities); (e) inspection and certificate of occupancy.