ADUs are allowed in FairfaxTypes:Internal
Types:Internal
Accessory Dwelling Unit (ADU) Rules for Fairfax, VA
Is your property eligible for an ADU?
# of Parcels
9,716
Zoning districts
16
Avg Parcel Value
$994,428
Median Parcel Size
0.24 acres
Zoning Districts:
9,704 parcels · 16 districts
RH
31%(3,011)
PD-M
17%(1,667)
RM
13%(1,273)
RMF
10%(975)
Other
29%(2,778)
ADU Rules
What can you build in Fairfax, VA?
Fairfax, VA follows state and local rules for Accessory Dwelling Units. Here is a concise overview of the local rules.
Eligibility
- –Internal / Attached ADU: By Right
- –Detached ADU: Not permitted
Interior / Attached ADU Size Limits
- –Maximum internal/attached ADU size is 35% of the principal dwelling’s gross floor area.
Max Units
- –1 ADU per single-family dwelling (internal/attached); detached not permitted.
- –0 ADUs per lot in duplex and townhouses (RT-6/RT), multifamily (RMF), and nonresidential districts.
Owner Occupancy
- –One dwelling, principal or ADU, must be owner-occupied.
Parking
- –No ADU-specific minimum; single-family dwellings require 2 spaces per unit. No ADU-specific maximum; ADU residents may have at most 2 vehicles.
Rental Restrictions
- –ADU cannot be rented as an independent dwelling to a separate tenant household; combined occupancy of the single-family dwelling and the ADU must be one household; if occupancy deviates from approved conditions, the space shall not be independently leased as a separate dwelling unit.
ADU State Law
What can you build in Virginia?
- –Virginia does not have a statewide ADU mandate; ADU rules are set by individual municipalities.
- –Building/fire codes are set statewide, but whether an ADU is allowed is local zoning.
- –SB 304 would have mandated ADUs. It passed the Virginia Senate in 2024 but was continued/left in House committee (i.e., not enacted statewide)
What's allowed on your lot?
These are the municipality-wide rules. What's allowed on a specific property also depends on state laws, setbacks, floor area ratio, lot coverage, environmental constraints, topography, and other property-specific factors. Search your address on FutureLot to see what's allowed on your property.
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