Fairfax County, VA Accessory Structures: ADU Owner Occupancy (2026)
Key Facts
- Owner-occupancy
- Required in ADU or main house
- Permit type
- Administrative permit
- Max occupants
- 2 people in ADU
- Enforcement
- Zoning Administrator
Summary
Fairfax County zoning requires that either the accessory living unit or the main house be owner-occupied, preventing owners from renting out both the ADU and the principal dwelling to tenants at the same time.
Either the accessory living unit or the principal dwelling unit must be owner-occupied.
(7) The accessory living unit may be occupied by no more than two people.
https://online.encodeplus.com/regs/fairfaxcounty-va/doc-viewer.aspx#secid--1 240/545 8/18/26, 9:54 PM Document Viewer | Zoning Ordinance
(8) The principal single-family dwelling unit may be occupied by not more than one of the following:
(a) Two or more persons related by blood or marriage and any number of their natural children, foster
children, stepchildren, adopted children, or children in kinship care;
(b) One or two persons with their dependent children, including natural children, foster children,
stepchildren, adopted children, or children in kinship care, functioning as a single household; or
(c) A group of not more than four persons not related by blood or marriage, functioning as a single
household.
(9) As specified in Article 6, a dwelling with an accessory living unit must provide the number of on-site
parking spaces required for the principal dwelling unit, plus one additional space. Only one space serving the lot must provide convenient access to the street.
Official source re-checked September 7, 2026: no newer edition of the code had been published.
Full Breakdown
Fairfax County allows one accessory living unit (ADU) per single-family detached lot by administrative permit, but subsection 4102.7.B(6) requires either the ADU or the principal dwelling to remain owner-occupied. This blocks investor purchases that rent out both units simultaneously. The ADU is capped at 800 square feet or 40% of the principal dwelling's floor area, limited to two bedrooms, and may house no more than two occupants. If owner-occupancy lapses, subsection (14) strips the ADU of its dwelling-unit status until the property again satisfies single-family occupancy rules.
Violations & Fines
Losing owner-occupancy voids the ADU's dwelling status; the unit may not be occupied as a dwelling until the property again meets single-family occupancy limits under subsection 4102.3.A.
Frequently Asked Questions
Can I rent out both my house and the ADU at the same time in Fairfax County?
What happens if owner-occupancy stops?
Sources & Official References
Other rules in Fairfax County
Compare Fairfax County to another location·View the Virginia accessory structures overview
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