Arlington County Zoning Regulations for Accessory Buildings and Sheds

According to the Arlington County Zoning Ordinance, no building or structure may be erected or constructed until the proper approval or permit has been obtained from the zoning administrator [Section 15.1.1.B]. While the ordinance generally requires permits for all structures, it establishes a critical threshold at 150 square feet: accessory buildings in Arlington County that are 150 square feet or smaller (and less than two stories tall) are exempt from being calculated as part of the total lot coverage percentage [Section 3.1.4.A.1(b)].

General Permit Requirements in Arlington County

The Arlington County Zoning Ordinance is explicit regarding the commencement of any construction project. Residents and developers must obtain "proper approval or a permit" before any wall, building, or structure is built, constructed, or altered [Section 15.1.1.B]. When applying for these permits, the Arlington County Zoning office requires the submission of plot plans drawn to scale that show the exact sizes and locations of all existing and proposed buildings [Section 15.1.2.A].

Size Thresholds and Lot Coverage

While Arlington County requires a permit process for structures, the size of an accessory building—such as a shed, gazebo, or detached garage—determines how it impacts the "Lot Coverage" limits of a property. Lot coverage is the percentage of the total lot area covered by the main building and specific accessory features [Section 3.1.4.A.1].

Accessory Building Coverage Standards

The following table outlines how the Arlington County Zoning Ordinance treats accessory structures based on their footprint and height:

Structure Size/Type	Counted Toward Lot Coverage?	Reference Section
Accessory building footprint 150 sq. ft. or less (and under 2 stories)	No	[§3.1.4.A.1(b)]
Accessory building footprint larger than 150 sq. ft.	Yes	[§3.1.4.A.1(b)]
Accessory building 2 stories or more (regardless of footprint)	Yes	[§3.1.4.A.1(b)]
Gazebos and pergolas (any size)	Yes	[§3.1.4.A.1(f)]

Placement and Setback Standards

The Arlington County Zoning Ordinance also uses size thresholds to determine where an accessory building can be placed on a lot. For accessory buildings in Residential (R) districts, the allowed setbacks change significantly once a structure exceeds 560 or 650 square feet [Section 3.2.6.A.2(c)(2)].

Setback Requirements for Small Accessory Buildings

To qualify for reduced setbacks, the structure must be lower than 1.5 stories (or 25 feet) and meet the following footprint limits:

R-5 and R-6 Districts: Footprint smaller than 560 square feet.
All Other R Districts: Footprint smaller than 650 square feet.

Placement Detail	Requirement	Reference Section
Distance from Main Building	Minimum 8 feet	[§3.2.6.A.2(c)(2)(i)]
Interior Lot: Eave to Side/Rear Line	Minimum 1 foot	[§3.2.6.A.2(c)(2)(ii)]
Corner Lot: Eave to Side Lot Line	Minimum 1 foot	[§3.2.6.A.2(c)(2)(iii)]
Corner Lot: Eave to Rear Lot Line	Minimum 10 feet	[§3.2.6.A.2(c)(2)(iii)]

If an accessory building in Arlington County is two or more stories tall, or taller than 25 feet, it may not occupy any part of a required rear yard and must stay at least 10 feet from any lot line [Section 3.2.6.A.2(c)(2)].

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