Setback Requirements for the R15-30T Townhouse Dwelling District

In the R15-30T district of Arlington County, residential developments are generally required to maintain a front and rear setback of 25 feet and a street-side setback of 15 feet. While by-right detached dwellings follow standard residential side yard requirements of 10 feet (reducible to 8 feet), special exception townhouse projects may utilize a reduced interior side setback of 7 feet for end units [Section 5.8.3, Section 3.2.6].

General Setback Standards for the R15-30T District

In Arlington County, the R15-30T: Townhouse Dwelling district is primarily regulated according to the standards of the R-5 district for by-right development, with additional specific criteria for projects approved by special exception [Section 5.8.1]. The following table outlines the dimensional requirements for the R15-30T district:

R15-30T Setback Requirements (Special Exception Projects)

Standard	Townhouse, Semidetached, and Existing One-Family Dwellings
Front Setback	25 feet
Side Setback (Interior)	7 feet (for end units)
Side Setback (Street/Corner)	15 feet
Rear Setback	25 feet

[Section 5.8.3.B]

R15-30T By-Right Setback Standards

For by-right development in the R15-30T district, structures must follow the placement rules established in Article 3 of the Arlington County Zoning Ordinance:

Yard Type	By-Right Detached Dwelling Requirement
Front Yard	25 feet (or the average of existing structures on the block)
Side Yard	10 feet minimum (one side may be reduced to 8 feet)
Aggregate Side Yards	Not less than 30% of the total lot width
Rear Yard	25 feet

[Section 3.2.6.A.1, Section 3.2.6.A.2]

Modifications and Special Conditions

Arlington County provides flexibility for setbacks in the R15-30T district to maintain neighborhood scale and respond to specific site conditions.

Neighborhood Scale and Average Setbacks

To ensure that new developments in the R15-30T district align with existing community patterns, the front yard setback for one-family and two-family dwellings may be reduced to the average setback of the existing buildings on the same side of the subject block [Section 5.8.4.A.2]. Additionally, for one-family dwellings, the distance between a street right-of-way and the front wall may be reduced to the average of existing structures on the same frontage, provided the absolute minimum distance is at least 15 feet [Section 3.2.6.A.1(e)].

Accessory Building Setbacks

Accessory buildings in the R15-30T district are subject to specific placement rules within Arlington County:

Side/Rear Separation: Additions to a main building must be at least eight feet from any wall of an existing accessory building [Section 3.2.6.A.2(c)].
Distance from Main Building: Accessory buildings taller than 25 feet or two stories cannot be closer than 15 feet to any wall of a main building [Section 3.2.6.A.2(c)(2)].
Street Setback: Accessory buildings must be located at least 25 feet from any street or officially designated street right-of-way line [Section 12.9.2.A.2(b)(3)].

Permitted Encroachments into Setbacks

Arlington County allows certain architectural features and structures to extend into the required setbacks of the R15-30T district.

Feature	Allowed Encroachment
Eaves, Trim, and Fascia	Up to 18 inches [Section 3.2.6.A.3(a)(1)]
Porches (Interior Lots)	4 feet into front/rear yard (no closer than 21 feet to R-O-W) [Section 3.2.6.A.3(a)(4)]
Porches (Corner Lots)	4 feet into front/street-side yard (no closer than 21 feet to R-O-W) [Section 3.2.6.A.3(a)(5)]
Balconies and Decks	Up to 4 feet [Section 3.2.6.A.3(a)(3)]
Steps and Stairs	Up to 4 feet [Section 3.2.6.A.3(a)(6)]
Bay Windows	Up to 18 inches [Section 3.2.6.A.3(a)(1)]

Sections Cited

§3.2.6 Placement
§5.8.1 R15-30T, Townhouse Dwelling District: Purpose
§5.8.3 R15-30T, Townhouse Dwelling District: Density and dimensional standards
§5.8.4 R15-30T, Townhouse Dwelling District: District use standards
§12.9.2 Accessory dwellings