ADU Pass
Herndon
No County portion
Also in: Fairfax County
ADU Pass helps homeowners in Herndon, 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
Two-tier authority: Town of Herndon zoning AND building permits (town runs full Community Development department). Herndon is the rare Northern Virginia incorporated town that retained its own building department rather than transferring to county (unlike Haymarket). ADU process: zoning verification, accessory-dwelling permit application, building permit, inspections, certificate of occupancy — all through Town of Herndon Community Development at 777 Lynn Street.
Cost scenarios
| Scenario | Sq ft | Permit | Build | Total |
|---|---|---|---|---|
| minimum | 200 | $950 | $96,000 | $96,950 |
| 600 | 600 | $1,850 | $288,000 | $289,850 |
| midpoint | 600 | $1,850 | $288,000 | $289,850 |
| maximum | 900 | $2,450 | $432,000 | $434,450 |
Fee breakdown (as of 2026-05)
Permitting process
Viability (permitted uses)
- Long-term rental: with-restrictions Strong long-term demand from Silver Line transit commuters, Dulles tech-corridor workers (Volkswagen Group, Northrop Grumman). Per Chapter 78 occupancy and registration requirements.
- Short-term rental: with-restrictions Herndon permits STRs subject to zoning compliance and Town transient occupancy tax registration. Strong STR demand from Dulles airport visitors, tech-corridor business travelers, and DC-area weekend tourism.
- Office rental: no Office rental to outside tenants not permitted in residential districts.
- Home office: yes Home occupation permitted under Herndon zoning.
- Studio / workshop: yes Personal studio is a permitted accessory use.
- Agriculture: no Herndon town limits are urban-suburban; agricultural accessory structures not generally permitted.
- Relative support: with-restrictions Multigenerational ADU use permitted per Herndon zoning.
Contacts
Utilities
- Water: Town of Herndon municipal water (town runs own utility) · 30d connect · $4,500 · separate meter required
- Sewer: Town of Herndon sewer collection, treatment via Fairfax County Wastewater · 45d connect · $9,000
- Electric: Dominion Energy Virginia (most parcels); some served by NOVEC · 28d connect · $2,400
- Gas: Washington Gas · 21d connect · $2,200
Property values & taxes
Construction timeline
Realistic total: best 9mo · typical 13mo · worst 20mo
Modular pathway inspectors are occasional with modular
Dulles Toll Road and Fairfax County Parkway provide major-route access; Herndon's older historic-district streets may constrain modular delivery for town-core lots.
Financing
Insurance impact
HOA prevalence & preemption
Herndon's older neighborhoods (Town center, Hiddenbrook) have low HOA presence; newer transit-oriented and Innovation Center area developments often have active HOAs.
Regulatory overlays (1)
- historic-district
Herndon Historic District (along Pine, Elden, and Lynn Streets) includes 1857-1920s building stock from the W&OD Railroad era. Some parcels subject to Architectural Review Board oversight for visible-from-public-way modifications.
Technical envelope (climate & building code)
Climate & energy code
Building code
Amendments:
- Amendment
- Amendment
- Amendment
Contractor market (aggregate)
Legal history (timeline)
Current ordinance: Town of Herndon Code Chapter 78 Zoning Ordinance, Article IV Accessory Uses and Structures, adopted 2019-01-01, last amended 2024-03-01
- 1858-01-01 — Town of Herndon incorporated (local-ordinance)
Town of Herndon incorporated in 1858; named for Commander William Lewis Herndon, lost at sea on the SS Central America (1857).
Effect: Establishes Herndon's incorporated authority to enact independent zoning. - 2019-01-01 — Town of Herndon Zoning Ordinance comprehensive (Chapter 78) (local-ordinance)
Town adopted modernized comprehensive Chapter 78 zoning ordinance with explicit accessory dwelling provisions.
Effect: Current operative town zoning code with explicit ADU framework; pre-2026 status likely exempts town from SB531. - 2022-11-15 — WMATA Silver Line Phase 2 opened with Herndon station (local-ordinance)
Metrorail Silver Line Phase 2 extended service to Herndon-Innovation Center stations, dramatically improving Herndon's transit access and influencing ADU demand.
Effect: Significant property-value uplift; enhanced rental demand from transit-oriented commuters. - 2026-04-13 — Virginia SB531 signed by Governor Spanberger (state-law)
Statewide ADU by-right mandate; effective July 1, 2027.
Effect: Herndon's 2019 Chapter 78 ADU provisions likely qualify as pre-2026 ordinance, exempting town from SB531.
Known issues (2)
- policy-review — Owners avoid the multi-agency coordination headache common to other VA incorporated towns; faster turnaround possible with focused Herndon staff.
- other — Strong ROI for ADUs within walking distance of Herndon or Herndon-Innovation Center stations.
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
- 20172
Post Office
- 590 Grove St, 20170