Garage conversion rules in Fairfax County, VA — sometimes called garage-to-ADU or accessory living unit conversions — govern permits, ceiling height, egress, and parking replacement.
Detached garages are allowed as accessory structures in all residential zones in Fairfax County, subject to setbacks (typically 5–10 ft from side/rear lines), height limits (15 ft or principal structure height), and lot coverage caps. Building permits are required. Detached garages may be converted to ALUs under the 2021 zMOD rules with additional permits. HOA architectural review typically required.
Detached garages in Fairfax County are regulated as accessory structures under Zoning Ordinance Article 4. Key requirements: (1) Setbacks — typically 5 ft from side and rear property lines in R-1 through R-8 zones, 10 ft in R-A, R-C, R-E; front yards not permitted. (2) Height — maximum 15 feet or the height of the principal dwelling, whichever is less (some zones allow up to 25 ft for architecturally integrated structures). (3) Lot coverage — the combined footprint of principal dwelling plus accessory structures must not exceed zone maximums (30–40% typical). (4) Size — accessory structures generally may not exceed 50% of the principal dwelling's footprint. All detached garages require a Fairfax County building permit through Land Development Services (USBC compliance), including foundation, framing, electrical, and final inspections. Plumbing (if a sink or bathroom is added) is permitted separately. Detached garages may be designed and permitted as garage-with-ALU-above, which qualifies as an Accessory Living Unit under 2021 zMOD rules. Garage conversion to living space requires permits, egress and ventilation upgrades, and conformance with USBC. Driveway access and impervious surface rules apply — new curb cuts require VDOT approval; impervious coverage limits trigger stormwater requirements in Chesapeake Bay Preservation Areas. HOA ARC approval is typically required, especially in managed communities like Reston and Burke Centre.
Contact your local code enforcement office for specific penalty information.
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See how Fairfax County's garage conversions rules stack up against other locations.
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