Warrenton — city ADU rules and incentives

ADU legality: allowed-with-restrictions

Stateunclear (Virginia accessory-dwelling framework (Dillon Rule))

Countywith-restrictions (Fauquier County Zoning Ordinance does not govern town-incorporated parcels)

Citywith-restrictions (Town of Warrenton Code of Ordinances Chapter 24 (Zoning), accessory-use and historic-district provisions)

Warrenton is the incorporated county seat of Fauquier County (population ~9,900) at the intersection of US 15, US 17, and US 29 in the Northern Virginia exurbs. The Town of Warrenton operates its own zoning ordinance for parcels inside town limits; Fauquier County zoning does not reach the town. The Warrenton Historic District (NRHP-listed) covers downtown including Old Town Warrenton, with architectural-review oversight. The town has its own water and sewer service. Strong commuter pull to Tysons / DC has driven property-value appreciation; the town is home to Highland Foundry, Wakefield School, and the Fauquier County Courthouse / government complex. STR registration and the town BPOL business license apply to short-term rentals.

City cost envelope

$194,650 all-in for a 600 sqft ADU (permit + build). Mid-size scenario.

Permit fee bundle: $2,500 (2026-04).

City viability (selected uses)

Long-term rentalyes

Short-term rentalwith-restrictions

Home officeyes

Relative supportyes

Fauquier County — county ADU rules and overlays

County ADU ordinance

Fauquier County permits one accessory dwelling unit per lot in residential and rural-ag districts subject to size, occupancy, and placement standards. The county's definition is strict: an ADU may be attached to, inside of, or detached from the principal dwelling, but no more than one ADU is allowed per lot and it may not be occupied by more than three persons or contain more than two bedrooms. Base size cap is 800 sqft. Lots of at least five acres in the RA (Rural Agricultural) or RC (Rural Conservation) districts may go up to 1,000 sqft, and where a legally existing pre-2013 dwelling in RA/RC on a five-plus-acre lot is being converted to the ADU the cap rises to 1,400 sqft or the existing unit's square footage (whichever is less). Detached ADUs require a side or rear external entrance. Fauquier's ordinance is unusually preservation-oriented: the 800-sqft base cap and the three-person occupancy limit are tighter than most Northern Virginia peers, reflecting the county's horse-country / agricultural-preservation zoning culture.

County regulatory overlays

Fauquier County administers four overlay regimes that bear materially on ADU projects: (1) a Floodplain Overlay District under Zoning Ordinance Section 4-400 tied to FEMA Special Flood Hazard Areas; (2) locally-adopted Historic Overlay Districts reviewed by the county's Architectural Review Board (distinct from the Commonwealth's Virginia Landmarks Register and the National Register); (3) an extensive network of conservation easements held by the Virginia Outdoors Foundation (VOF), Piedmont Environmental Council (PEC), and the Northern Virginia Conservation Trust (NVCT) on RA and RC parcels, which typically pre-empt ADU rights even where zoning would otherwise permit; and (4) the county's Service District framework (Bealeton, Catlett, Marshall, Midland, New Baltimore, Opal, Remington, Warrenton) inside which development standards are tuned for higher density and public utility connection. Fauquier has no coastal-commission jurisdiction, no CalFire-equivalent WUI regime (Virginia has no statewide wildland-urban-interface overlay), and no seismic-retrofit overlay.

Floodplain Overlay District
Fauquier County Historic Overlay Districts
Conservation Easement Overlay (VOF, PEC, NVCT-held easements)
Service District framework (Bealeton, Catlett, Marshall, Midland, New Baltimore, Opal, Remington, Warrenton)

County permitting (unincorporated parcels)

Fauquier County's Department of Community Development issues ADU building permits for every parcel in the county except those inside the Town of Warrenton (which operates its own zoning and building department). Unincorporated CDPs (Bealeton, Catlett, Marshall, Midland, New Baltimore, Opal, Remington outside the town limits, and the eight other service districts) all route through the county's building division. A typical ADU permit bundle includes: (1) a Zoning Permit confirming use and dimensional compliance, (2) a Building Permit with stamped plans, (3) Electrical, Plumbing, and Mechanical trade permits, (4) a Virginia Department of Health (VDH) - Fauquier Environmental Health construction permit for well and/or septic on parcels not served by public water or sewer, (5) a Floodplain Development Permit if any portion of the parcel is within the Floodplain Overlay District (Section 4-400), and (6) a Historic District Certificate of Appropriateness if the parcel is in a designated Fauquier Historic Overlay District.

Virginia state — ADU law and programs

State ADU law

Virginia has NOT enacted a statewide ADU preemption law. Virginia is a Dillon Rule state — localities possess only those powers expressly granted by the General Assembly — and the statutes granting zoning authority (Va. Code § 15.2-2280 et seq.) leave ADU regulation to local ordinances. ADU permission, setbacks, parking, size, and owner-occupancy rules therefore vary by county, independent city, and town. Virginia is unique in that it has 38 independent cities that function as counties (neither in nor subordinate to the surrounding county), meaning 'the county' for any given Virginia property may be an independent city rather than a true county. Several ADU preemption bills have been introduced in recent General Assembly sessions (2022 through 2025) without enactment; none have advanced past committee as of the Assembly's 2026 regular session adjournment.

State financing programs

Virginia does not operate an ADU-specific statewide loan, grant, or forgivable-loan program. Virginia Housing (formerly the Virginia Housing Development Authority, VHDA — rebranded 2020) administers general first-time-homebuyer, down-payment-assistance (DPA), mortgage-credit-certificate, and rehabilitation products that can be applied to ADU-adjacent purchases or improvements when eligibility criteria are met, but none target ADU construction as a distinct product. The Virginia Department of Housing and Community Development (DHCD) administers federal HOME and CDBG pass-through funds that local jurisdictions can direct toward ADU-adjacent rehab, but there is no state-level ADU-dedicated line item. Federally available products (FHA 203(k), Fannie Mae HomeReady and HomeStyle Renovation, Freddie Mac CHOICERenovation) remain the primary ADU financing path for Virginia homeowners.

State housing programs

Virginia does not run a state-level pre-approved-ADU-plan catalog, statewide impact-fee-waiver statute for ADUs, or streamlined-review mandate. State-level programs that touch ADU-adjacent policy are coordinated primarily through the Department of Housing and Community Development (DHCD) and Virginia Housing, and act by funding or assisting local jurisdictions rather than by preemption. Local ADU activity — Arlington County's Accessory Dwellings program (detached ADUs permitted since 2008, liberalized 2020), Alexandria's accessory-dwelling ordinance, Fairfax County's accessory-living-unit program, and Charlottesville's 2021 zoning-code changes — is authorized under the localities' Va. Code § 15.2-2280 zoning authority, not by state mandate.

DHCD Community Development Block Grant (CDBG) Program — Federal CDBG funds administered by DHCD to eligible non-entitlement Virginia localities for community-revitalization, housing-rehab, and infrastructure projects. Not ADU-specific. Participating localities can direct CDBG funds toward housing-rehab projects where local policy supports ADUs.
DHCD HOME Investment Partnerships Program — Federal HOME funds administered by DHCD to Virginia participating jurisdictions and non-profits for affordable-housing acquisition, rehab, and new construction. Not ADU-specific; can be directed to ADU-adjacent rehab at local discretion.
Virginia Housing Commission — Permanent advisory commission of the General Assembly that studies housing-policy questions and recommends legislation. Has periodically studied ADU preemption and missing-middle housing without recommending statewide enactment as of 2026-04-21.
Local ADU ordinances under Va. Code § 15.2-2280 authority — Not a state program — listed here because Virginia ADU policy is executed entirely at the locality level under the § 15.2-2280 zoning grant. A homeowner seeking to build an ADU consults the zoning ordinance of the specific county, city, or town where the parcel is located.

Federal (United States) — ADU-relevant rules and programs

Federal ADU law

The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.

Federal financing programs

Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.

Federal tax credits

There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.

Federal housing programs

HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.

Warrenton Carrier Annex