Setback Requirements for the S-3A Special District in Arlington County

In the S-3A, Special District of Arlington County, structures are generally required to be set back a minimum of 25 feet from any street right-of-way line. Side and rear yard requirements for one-family dwellings in this district are typically 10 feet, while other permitted structures must follow a formulaic setback based on the total height of the building [§3.2.6.A].

Overview of the S-3A, Special District

The Arlington County S-3A, Special District is established to encourage the retention of properties in a relatively undeveloped state, such as active or passive recreation areas, scenic vistas, and stream valley floodplains [§4.2.1]. Because this district allows for a variety of uses ranging from one-family dwellings to institutional facilities like schools and hospitals, the setback requirements vary based on the specific use and the dimensions of the structure [§4.1.2, §4.2.3].

Street (Front) Setback Requirements

Setbacks from the street in the S-3A, Special District are determined by the type of structure and its proximity to the street centerline. Arlington County regulations specify that no structure may be closer to the centerline of a street than 50 percent of the building's height [§3.2.6.A.1].

Use Category	Minimum Street Setback
One-family Dwellings	25 feet from the street right-of-way line [§3.2.6.A.1(e)]
All Other Permitted Uses	The larger of: 50 feet from the street centerline OR 25 feet from the street right-of-way line [§3.2.6.A.1(d)]

Side and Rear Setback Requirements

Side and rear yard requirements in the Arlington County S-3A, Special District ensure adequate spacing between structures and property lines to provide light, air, and privacy [§3.2.1].

Use Category	Side/Rear Setback Standard
One-family Dwellings	10 feet (one side may be reduced to 8 feet). The aggregate width of both side yards must be at least 30% of the lot width. Interior lots must be at least 25 feet from the rear lot line [§3.2.6.A.2(b)]
Other Residential/Non-Residential	10 feet, plus 1 additional foot for every 2.5 feet of building height above 25 feet. On interior lots, the structure must be at least 25 feet from the rear lot line [§3.2.6.A.2(e)]
Accessory Buildings	Generally must be at least 8 to 15 feet from the main building depending on height/stories; eave requirements apply for property lines [§3.2.6.A.2(c)]

Permitted Setback Encroachments

Arlington County allows certain architectural features and minor structures to project into the required setbacks of the S-3A, Special District, including but not limited to [§3.2.6.A.3]:

Cornices, eaves, and chimneys: May encroach up to 18 inches.
Unenclosed balconies, decks, and patios: May encroach up to 4 feet, but must remain at least 5 feet from any property line.
Porches: May encroach 4 feet into the front and rear yards, provided they are no closer than 21 feet to any street right-of-way line.
Steps and Stairs: May encroach into yards provided they are at least 5 feet from any lot line (stairs less than 8 inches above grade may reach the lot line).
Fences and Walls: Fences up to 4 feet high are permitted in street setbacks, and up to 7 feet in side or rear yards [§3.2.6.A.3(e)].

Special Modifications for Schools

For elementary, middle, and high schools located within the S-3A, Special District, the Arlington County Board may modify the standard setback and placement requirements via a use permit [§4.2.4.A.2]. These modifications are considered when the school development project's scale and massing are compatible with the surrounding neighborhood and the design facilitates efficient transportation and environmental sustainability [§4.2.4.A.3].

Sections Cited