Local Permitting Guide

2026 Virginia ADU Law: What Actually Changes for Northern Virginia

Virginia passed a new statewide law (SB 531) in 2026 requiring localities to allow Accessory Dwelling Units by right. It's a significant change for most of the state — but if you live in Fairfax County, Arlington, or Alexandria, the headline is more nuanced than "ADUs are now legal everywhere." Here's what the law actually does, and doesn't do, for Northern Virginia homeowners specifically.

What SB 531 Does Statewide

Effective July 1, 2027, the law establishes a statewide floor for ADU rules:

• By-right approval — localities must approve qualifying ADU permits administratively, without requiring special use permits or public hearings
• Lot size cap — localities cannot require lots larger than 6,000 sq ft for single-family zones to qualify
• Size standard — ADUs generally cannot exceed 1,000 sq ft or 50% of the primary dwelling's floor area, whichever is less
• No family-relation requirement — owners are not required to be related to ADU occupants
• Permit fees capped at $500 under the state framework

The Important Exemption

SB 531 exempts localities that already had their own ADU ordinance in place as of January 1, 2026. Fairfax County, Arlington County, and the City of Alexandria all had existing ADU ordinances before that date — meaning none of them are automatically required to adopt the new statewide framework. Each continues to operate under its own, separately established rules.

This doesn't mean ADUs are unavailable in these jurisdictions — quite the opposite, all three have permitted ADUs for years. It means the specific size limits, setbacks, and approval process vary by jurisdiction rather than following the new state standard.

What This Means If You're Planning an ADU

If you're in Fairfax County, Arlington, or Alexandria, your local jurisdiction's existing rules apply now and will continue to apply after July 2027 unless that locality separately chooses to update its ordinance. If you're in a Northern Virginia locality without a prior ADU ordinance — Loudoun County and Prince William County, for example — the new statewide framework will apply starting July 1, 2027.

Either way, the practical steps are the same: confirm your zoning district's specific rules, prepare a compliant site plan, and go through your locality's permit process. A local design-build team that has actually pulled permits in your specific jurisdiction can save real time here — the terminology, forms, and review process differ enough between Fairfax, Arlington, and Alexandria that experience in one doesn't fully transfer to another.