Virginia's ADU Law (SB 531): The Complete 2027 Guide
Virginia legalized backyard homes on nearly every single-family lot in the state. Here's exactly what SB 531 does, when it starts, what your county can still control, and how to be first in line.
In short: Effective July 1, 2027, Virginia Senate Bill 531 makes accessory dwelling units (ADUs) permitted by-right on single-family lots statewide. Localities must allow at least one ADU per single-family lot, cap the permit fee at $500, cannot impose setbacks stricter than those for the primary home, and can no longer require ADU occupants to be family members. The bill was signed into law in April 2026 and sponsored by Sen. Kannan Srinivasan (D‑Loudoun) and Sen. Saddam Salim (D‑Fairfax).
What does "by-right" actually mean?
By-right means your locality cannot use discretion to deny an ADU on a single-family lot. Before SB 531, many Virginia counties required a special-use permit, a public hearing, or a large minimum lot — any of which could be denied. After July 1, 2027, a compliant ADU application must be approved through the normal building-permit process. You still pull permits and meet code; the county simply can't say "no" to the concept.
The five things SB 531 changes
1. By-right approval
At least one ADU allowed per single-family lot, statewide — no discretionary denial.
2. $500 fee cap
The local permit fee for an ADU is capped at $500, ending sky-high review fees.
3. Fair setbacks
ADU setbacks can be no stricter than those already applied to your primary home.
4. Rent to anyone
The old family-relation requirement is removed — you can rent to any tenant.
5. Every locality
Applies to all Virginia cities and counties, including those that banned ADUs.
What stays local
Building code, safety, size and height caps, and reasonable design standards.
What your county can still control
SB 531 sets a statewide floor, not a ceiling. Localities keep authority over the building code, health-department septic approvals, maximum ADU size and height, and reasonable design and safety standards. That's why two lots in different counties can have very different ADU rules even after 2027 — and why a site-specific review matters. We track each locality's rules in our county rules database.
Why start before July 2027?
The law takes effect on a single day, and demand will spike immediately. Designing an ADU, engineering it, and getting permit-ready plans typically takes months. Homeowners who prepare during the 2026–2027 runway can submit the moment by-right applies — ahead of the rush, before 2027 demand pushes build costs up, and earning rental income sooner. Waiting until the law is live means joining the back of a very long line.
How much does an ADU cost in Virginia?
As a planning range, garage or interior conversions often run $60,000–$150,000, and new detached backyard homes typically run $180,000–$400,000+, or roughly $250–$400 per square foot depending on size, site conditions, and finishes. Your actual number depends on utilities, grading, and design — which is what a site-specific Readiness Assessment establishes.
How we help you prepare
Start with a free Quick-Fit Check to see whether your lot is a realistic candidate. If it is, a paid Readiness Assessment confirms zoning, utilities, setbacks, budget, and timeline for your specific parcel. From there, we design, permit, and build — one accountable team, concept to keys.
Take the Free Quick-Fit Check →
Frequently asked questions
What is Virginia SB 531?
SB 531 is a Virginia law, effective July 1, 2027, that makes accessory dwelling units permitted by-right on single-family lots statewide, caps permit fees at $500, sets fair setbacks, and removes the family-occupancy requirement.
Does SB 531 apply to every Virginia county?
Yes — it applies to all Virginia localities. Counties keep control over code, safety, size, height, and reasonable design standards, but can't deny an ADU outright on a single-family lot.
Do I need to wait until July 2027 to start?
No. Because design and permitting take months, preparing permit-ready plans now positions you to build first once the by-right rules take effect.
Can I build a detached backyard cottage, or only an interior unit?
SB 531 covers ADUs broadly, but some counties currently limit detached units. Many are updating their rules for 2027. Check your locality in our county database or ask us.
See if your property qualifies under SB 531.
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