ADU Pass
Mount Vernon
ADU Pass helps homeowners in Mount Vernon, No County, Virginia navigate the permit paperwork for building an accessory dwelling unit. This area covers 1 ZIP code.
Map
ADU details
ADU legality: allowed-with-restrictions
An ALU at a Mount Vernon parcel requires Fairfax County Administrative Permit (or Special Permit if detached), building permit, and likely no septic-system review (most parcels are on Fairfax Water and county sewer). George Washington Memorial Parkway proximity may trigger NPS / Section 106 review for parcels in the parkway's visual corridor. Shoreline parcels along the Potomac trigger CBPA RPA review.
Cost scenarios
Fee breakdown (as of 2026-05)
Permitting process
Viability (permitted uses)
- Long-term rental: with-restrictions Permitted with limits on occupancy; ALU must be subordinate to the principal dwelling and may carry owner-occupancy requirements.
- Short-term rental: no Fairfax County's ALU framework explicitly prohibits short-term rental use of the ALU. STR demand in the Mount Vernon CDP exists (estate visitors) but cannot be served by an ALU under current rules.
- Office rental: no Commercial office rental in an ALU is not contemplated by the ordinance.
- Home office: with-restrictions Home occupation by the owner is permitted under standard county conditions.
- Studio / workshop: yes Personal studio use by the owner is a normal accessory use.
- Agriculture: no Mount Vernon is suburban residential; agricultural ADU uses are not contemplated.
- Relative support: yes Family-occupancy ALU is the canonical use case the Fairfax County rules contemplate, particularly for elder parents and adult children.
Incentives
Contacts
Staff: Planner of the Day (First-contact zoning interpretation) ORDAdmin@fairfaxcounty.gov, PLUS Support Team (Permit portal support) PLUSSupport@FairfaxCounty.gov
Utilities
- Water: Fairfax Water (public water service in the Mount Vernon CDP)
- Sewer: Fairfax County Wastewater Management (public sewer service throughout the Mount Vernon CDP)
- Electric: Dominion Energy Virginia
- Gas: Washington Gas
Property values & taxes
Construction timeline
Modular pathway Virginia Industrialized Building Safety Law (IBSL) · inspectors are occasional with modular
Suburban Fairfax County access via I-95, US Route 1 (Richmond Highway), and the GW Memorial Parkway. Parkway has weight and width restrictions for commercial vehicles. Interior-ALU rule limits modular's relevance.
Financing
Insurance impact
High-value Mount Vernon properties carry above-average premiums; ALU rental use increases liability exposure.
HOA prevalence & preemption
Mount Vernon has significant HOA density in newer subdivisions (Mount Vernon Manor, Stratford Landing, Hollin Hills among others); HOA covenants frequently restrict ALU rental use beyond what county zoning allows.
Regulatory overlays (3)
- historic-district
Mount Vernon (the estate) is a designated National Historic Landmark, with the George Washington Memorial Parkway providing a federally-managed visual corridor. ALU work on parcels in the parkway's view-shed may require NPS coordination or Section 106 review for federally-funded projects. - wetland-overlay
Chesapeake Bay Preservation Act RPA applies to Potomac shoreline parcels in the Mount Vernon CDP. 100-foot disturbance buffer from mean high water and tidal wetlands; this affects parcels along the river and Little Hunting Creek. - airport-noise-zone
Mount Vernon lies under the southern approach to Reagan National Airport (DCA) and the southwestern approach to Joint Base Andrews; some parcels are within the 65 DNL noise contour.
Technical envelope (climate & building code)
Climate & energy code
Building code
Legal history (timeline)
Current ordinance: Fairfax County Zoning Ordinance — Accessory Living Unit (ALU) provisions
- 1858-04-06 — Mount Vernon Ladies' Association purchase of 200 acres of the original 8,000-acre Washington estate (other)
Establishes the Mount Vernon Ladies' Association as the perpetual private owner of the historic estate adjacent to the CDP.
Effect: Creates a permanent non-county heritage-preservation neighbor that influences zoning review for adjacent ADU work in the visual corridor. - 2024-01-18 — Virginia Uniform Statewide Building Code (USBC) 2021 edition adopted (state-law)
Virginia DHCD adoption of the 2021 IRC/IBC base with Virginia amendments.
Effect: Sets the technical envelope (egress, R-values, ventilation) any Mount Vernon ADU must be built to. - 2026-01-01 — Fairfax County Accessory Living Units Proposed Zoning Ordinance Amendment review begins (county-ordinance)
Fairfax County initiated a review of the ALU rules in 2026 after observing only ~160 approvals in four years. Any amendment will move through county advisory bodies, Planning Commission, and Board of Supervisors.
Effect: May relax the interior-only constraint, increase permitted size, or add a detached-unit pathway for Mount Vernon parcels. - 2026-04-14 — Virginia SB531 signed by Governor Spanberger — statewide ADU mandate (state-law)
Statewide by-right ADU framework with delayed effective date July 1, 2027. $500 permit-fee cap, no-stricter-setback rule, standardized ADU definitions. Pre-January-2026 local ADU ordinances exempt.
Effect: Fairfax County's existing ALU framework predates 2026 and likely qualifies as an exempting ordinance, but the interior-only constraint may face state-level preemption challenges if SB531 standardization is interpreted to require detached-ADU availability.
Known issues (1)
- policy-review — Fairfax County is reviewing its ALU rules in 2026 due to extremely low uptake (~160 approvals in 4 years). Outcome may add a detached-ADU pathway. SB531 (effective July 2027) may force changes if the county's interior-only rule is deemed non-conforming. (source)
County: no attribution (synthetic bucket)
No county
This city sits in the state's "no county" bucket — its ADU rules derive directly from state law and city ordinance without a county intermediary. No county-level sections apply.
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.
ZIP Code
- 22121
Post Office
- 3500t Mount Vernon Memorial Hwy, 22121