Buying Land in Fairfax County, Virginia

A dense, suburban D.C. county -- with one narrow rural exception

Fairfax County is Virginia's most populous county, a core part of the Washington, D.C. metropolitan area, and overwhelmingly suburban to urban in character across the vast majority of its land area. For nearly any parcel in the county, buying land means an infill lot, a teardown, or a redevelopment site inside an already-dense built environment -- not raw acreage or farmland, and not a market where septic feasibility or perc-test results are typically the deciding factor.

The one genuine exception is the county's far-western edge, toward the Loudoun County line, where lower density and some working agricultural land survive -- reflecting the county's own R-A Rural Agricultural zoning district, described below. Even there, treat this as a narrow, geographically limited exception to Fairfax's dominant suburban character rather than a broad rural land market; a buyer specifically seeking rural acreage at scale will generally find far more of it in neighboring Loudoun or in counties further from the D.C. core covered elsewhere on this site.

Data centers, not rural zoning, are the county's defining land-use fight

Fairfax County borders Loudoun County's "Data Center Alley," the world's largest concentration of data centers, and that proximity has made data-center siting the single most consequential and current zoning story in the county -- far more so than the narrow rural R-A exception described below. In September 2024 the Board of Supervisors adopted a Data Centers Zoning Ordinance Amendment setting by-right size caps (40,000 square feet in C-3/C-4, 80,000 in I-2/I-3/I-4) and requiring a Special Exception for anything larger, and in March 2026 the county sold 41.7 acres of a Chantilly police-training site to a data-center developer for $166.8 million. See our dedicated zoning page for Fairfax County for the full picture, including an active substation dispute on the Alexandria border and the county's separate, higher tax rate on data-center equipment.

The R-A Rural Agricultural and R-C Residential-Conservation districts

Away from the data-center corridor, Fairfax County's zoning ordinance also includes an R-A Rural Agricultural district, established specifically to identify land used for farming or livestock and to keep that land from urban-style development, and a separate R-C Residential-Conservation district. Notably, the county's cluster-development provisions -- which in other residential districts allow smaller individual lots in exchange for 25% to 50% of a subdivision's total area (30% for approved cluster subdivisions generally) being preserved as open space -- do not apply within the R-A district itself. This research pass could not independently confirm the current R-A district's minimum lot size or complete by-right-versus-special-permit use list from search-indexed sources -- confirm those figures directly with the county's Department of Planning and Development before assuming any specific number for a western-Fairfax parcel.

Septic and wells: the county's own Health Department, not a shared VDH district

Unlike most rural Virginia counties, which share a multi-county Virginia Department of Health health district, Fairfax County operates its own dedicated Health Department, whose Onsite Sewage and Water Program administers both state and local regulations for septic systems and private wells countywide. Applications run through the county's Planning and Land Use System (PLUS), and the county's own Private Well Water Ordinance (Chapter 70.1 of the Fairfax County Code) was last amended by the Board of Supervisors on February 7, 2005. The Environmental Health Services office is located at 10777 Main Street in Fairfax (703-246-2201) -- but given that virtually all of the county outside the narrow western rural edge is already served by public water and sewer, septic and well permitting is a realistic consideration only for that limited area.