ADU Pass
Dulles
No County portion
Also in: Loudoun County
ADU Pass helps homeowners in Dulles, No County, Virginia navigate the permit paperwork for building an accessory dwelling unit. This area covers 1 ZIP code.
ADU details
ADU legality: allowed-with-restrictions
Attached ADUs by-right in qualifying zones with public water/sewer (common in eastern Loudoun including the Dulles area). Detached ADUs require special exception. Minimum 800 sqft cap or 35 percent of principal-dwelling floor area, whichever is greater. Note: Loudoun's 'ADU Purchase Program' refers to Affordable Dwelling Units (income-restricted housing), which is separate from the accessory-dwelling-unit zoning rule.
Cost scenarios
| Scenario | Sq ft | Permit | Build | Total |
|---|---|---|---|---|
| minimum | 200 | $2,400 | $92,000 | $94,400 |
| 600 | 600 | $2,400 | $276,000 | $278,400 |
| midpoint | 500 | $2,400 | $230,000 | $232,400 |
| maximum | 800 | $2,400 | $368,000 | $370,400 |
Fee breakdown (as of 2026-05)
Permitting process
Viability (permitted uses)
- Long-term rental: yes Long-term rental (30+ days) of permitted ADU is by-right under Loudoun zoning. No owner-occupancy mandate at the county level.
- Short-term rental: with-restrictions Loudoun requires short-term rental registration with Commissioner of the Revenue; transient occupancy tax applies. Some HOAs and PD zones (common around Dulles) prohibit STR by covenant.
- Office rental: with-restrictions Detached office rental to third parties not permitted under residential zoning; would require commercial rezoning.
- Home office: yes Owner home occupation permitted in ADU subject to Loudoun home-occupation rules (no visible signage, limited customer traffic, no employees on site).
- Studio / workshop: yes Personal artist/musician studio is a permitted accessory use; no separate permit required.
- Agriculture: with-restrictions Dulles CDP is largely PD (planned development) zoning where agriculture is limited. Western edges abut AR-1/AR-2 where ADU as farm-worker housing has its own pathway.
- Relative support: yes Multigenerational/family-member occupancy of ADU is explicitly permitted; no rental registration required.
Contacts
Utilities
- Water: Loudoun Water · 45d connect · $8,500
- Sewer: Loudoun Water · 45d connect · $9,500
- Electric: Dominion Energy Virginia (also NOVEC in parts of western Dulles area) · 30d connect · $2,200
- Gas: Washington Gas · 45d connect · $2,800
Property values & taxes
Construction timeline
Realistic total: best 9mo · typical 13mo · worst 20mo
Modular pathway inspectors are occasional with modular
Route 28 and Dulles Greenway provide good wide-load access; Dulles Toll Road / Greenway have height restrictions; route surveys typically required for modular sections over 13 ft 6 in tall.
Financing
State ADU loans:
Insurance impact
HOA prevalence & preemption
Dulles CDP is dominated by planned-development communities; HOA covenants commonly restrict ADUs more strictly than county zoning. Virginia POAA (Va. Code 55.1-1800 et seq.) does not preempt HOA ADU bans.
Regulatory overlays (1)
- airport-noise-zone
Dulles CDP underlies the IAD Airport Influence Area and FAR Part 77 imaginary surfaces. New residential construction within 65 DNL noise contour requires acoustical treatment per Loudoun zoning.
Technical envelope (climate & building code)
Climate & energy code
Building code
Amendments:
- Amendment
- Amendment
- Amendment
Contractor market (aggregate)
Legal history (timeline)
Current ordinance: Loudoun County Zoning Ordinance, Section 5.02 Accessory Dwelling Units, adopted 2023-12-12, last amended 2024-01-01
- 2023-12-12 — Loudoun County Zoning Ordinance Rewrite adopted (county-ordinance)
Comprehensive zoning rewrite (effective January 2024) consolidated ADU rules under new Chapter 5 use standards. Detached ADUs continued to require special exception in most residential districts.
Effect: Modernized Dulles-area ADU regulation under new ordinance structure; preserved special-exception requirement for detached units. - 2024-02-13 — SB 304 (Salim) statewide ADU mandate (state-bill)
Bill proposed statewide right to build one ADU on single-family residential lots; passed Senate but did not advance in House.
Effect: Would have preempted Loudoun's special-exception requirement for detached ADUs; failed to enact, local rule continues to govern Dulles.
Known issues (2)
- policy-review — Adds 6-12 months and several thousand dollars to detached-ADU project timelines.
- other — Adds approximately $8,000 to $15,000 to ADU build cost in noise-affected areas.
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
- 20146
Post Office
- 44715 Prentice Dr, 20101
Locale Names
- Ashburn