Rental conversions in Northern Virginia

A Virginia law enacted in 2026 and taking effect July 1, 2027 makes ADUs a permitted accessory use in single-family zoning districts, though it does not apply to localities that adopted an ADU ordinance before January 1, 2026.¹² Fairfax County staff say Virginia's 2026 accessory dwelling unit law, which takes effect July 1, 2027, does not apply to Fairfax County, because it exempts localities that adopted an ordinance before January 1, 2026.¹ For a house in Fairfax County, the county's own zoning ordinance is the one to read, and the state law's limits on parking and owner-occupancy rules don't reach it.

Fairfax County has proposed changes to its accessory living unit rules, with public hearings before the Planning Commission on October 29, 2026 and the Board of Supervisors on November 17, 2026.¹³ As proposed in 2026, Fairfax County's amendment would raise the size cap for an accessory living unit to 1,200 square feet or 40 percent of the main house, whichever is less, allow three occupants instead of two, drop the owner-occupancy rule and the extra parking space, and allow a detached unit by right on lots of at least 36,000 square feet.¹⁰

Until the Board of Supervisors votes, design to the current limits, or ask the company for a layout that would work under either set of rules.

Fairfax County requires any new outside entrance for an accessory living unit to be on the side or rear of the house, and the unit must connect to the main house through finished, heated and cooled, fully enclosed interior space.⁴ On a sloping lot with a walkout basement, the existing rear door can often serve as the unit's entrance; in a fully buried basement, a new areaway and door at the side or back is a bigger structural job.

Fairfax County currently requires either the accessory living unit or the main house to be owner-occupied, and the lot to have the parking required for the house plus one more space.⁴ The county checks those spaces on the plat filed with the application, so mark them before you apply and keep them clear afterward.

The 2021 IRC requires the units of a two-family dwelling to be separated by walls and floors with at least a 1-hour fire-resistance rating, or a 1/2-hour rating if the building has an automatic sprinkler system throughout.¹⁴ Ask the building department early whether your unit will be reviewed as part of a single-family house or as a second dwelling, since the fire separation it needs follows from that answer.

A Fairfax County accessory living unit must have a working multi-purpose fire extinguisher, and smoke detectors, plus carbon monoxide detectors where a fireplace or gas service requires them, interconnected with the main house.⁴ In Fairfax County, an emergency escape and rescue opening is required in the basement of a house built after October 1, 2003 and in every basement bedroom whatever the house's age; older basements may be finished without one, though the county strongly recommends it.¹⁵

Under Fairfax County's current standards, an interior accessory living unit may be no larger than 800 square feet or 40 percent of the main house, whichever is less, or the whole basement as it stood on July 1, 2021; it may have no more than two bedrooms and no more than two occupants.⁴ The occupant cap counts people rather than leases, so under the current rules a couple with a child would already be over it.

EPA's lead renovation rule generally doesn't cover homeowners working on their own pre-1978 homes, but it does apply if you rent out all or part of your home.¹⁶ With 44%¹⁷ of Fairfax County homes built before 1980, a lot of lower levels with original paneling and painted trim come under that rule once a tenant moves in.

Before a renter signs a lease for most pre-1978 housing, federal law requires the landlord to disclose known lead-based paint and hazards, share available records, hand over EPA's Protect Your Family From Lead pamphlet and include a Lead Warning Statement.¹⁸

Fairfax County's Department of Code Compliance treats work done without the proper permits or inspections, including a finished basement or attic, as unpermitted construction; a notice of violation allows a set period to get the permits and inspections, and work permitted after the fact must pass all of them.¹⁹ Bringing an existing lower-level apartment into line may mean opening some walls so an inspector can see the wiring and plumbing, so price that possibility before you count on the rent.

More than one in four adults 65 and older fall each year.²⁰ If the unit is for an aging parent, put the bedroom, a curbless shower and the entrance on one level, and keep the doorways wide enough for a walker. On a walkout lot that can mean no stairs at all between the car and the bed. NAHB's Certified Aging-in-Place Specialist (CAPS) credential trains remodelers in home modifications for aging in place.²¹

Calling the number on this page connects you, on a recorded line, to one independent company that handles rental conversions in the Northern Virginia area. You work out the layout, the schedule and the price with that company directly.

The company pays us for the call; you pay us nothing, and we never call or text you. How we make money

Look the company up in Virginia's license records before you sign. Virginia's Department of Professional and Occupational Regulation advises hiring only licensed contractors, and its License Lookup shows a license's status and any past disciplinary actions.²² Virginia's Board for Contractors licenses contracting businesses as Class A, B or C; the class sets the dollar value of jobs a firm may take on, and its classification or specialty sets the type of work it may do.²³ Check a Virginia license

Decide who will file the building permits. Owners may get Fairfax County permits in their own name, but the county strongly recommends that a properly licensed contractor pull them as the responsible party.²⁴