Arlington County Accessory Dwelling Unit (ADU) Parking Requirements

In Arlington County, a dedicated off-street parking space is generally required for an Accessory Dwelling Unit (ADU) if the property currently has no off-street parking. This requirement is waived if a County-conducted parking survey determines that the specific block where the dwelling is located is less than 65% parked. If off-street parking already exists on the Arlington County property, the owner must maintain either all existing spaces (up to two) or at least two spaces if more than two currently exist [Section 14.3.7].

General Parking Standards for ADUs

Parking requirements for accessory dwellings in Arlington County are determined by the existing parking conditions of the lot at the time of the ADU permit application. These regulations apply to all Residential (R) districts where accessory dwellings are permitted by-right, including R-5, R-6, R-8, R-10, R-20, R-10T, R15-30T, and R2-7 [Section 5.1.4].

Table 1: ADU Parking Creation and Maintenance Requirements

The following standards dictate when new parking must be built or when existing parking must be preserved for an ADU in Arlington County:

Existing Parking Condition	Requirement for Accessory Dwelling Unit (ADU)
Zero (0) existing off-street spaces	One (1) new space must be created (unless the 65% occupancy waiver applies)
One (1) or Two (2) existing off-street spaces	All existing off-street spaces must be maintained
More than Two (2) existing off-street spaces	At least two (2) off-street spaces must be maintained

[Section 14.3.7]

Parking Requirement Waivers

Arlington County provides an exemption for the creation of a new parking space based on neighborhood parking availability. If a property in an Arlington County Residential (R) district has no existing off-street parking, the owner is not required to create a new space for the ADU if a parking survey determines that the occupancy of on-street parking spaces on the block is less than 65% [Section 14.3.7].

Location and Design Standards

Parking spaces provided for ADUs in Arlington County must meet specific location and dimensional criteria to ensure they do not negatively impact the public right-of-way or the residential character of the neighborhood.

Encroachment: Parking spaces for dwellings in Residential (R) districts may encroach on the exterior 10 feet of a setback area, provided they are located on a driveway with an existing or approved curb cut [Section 14.3.3.I.1].
Maneuvering: With the exception of one-family and two-family dwellings, street rights-of-way shall not be used for maneuvering or direct ingress/egress to off-street parking spaces [Section 14.3.3.H.1].
Surface Material: The ground surface of the parking space must be paved with a durable, dust-free, and hard material, such as bituminous hot mix, Portland cement concrete, or an approved alternate material [Section 14.3.3.I.1].
Dimensions: Any new parking space created must meet the minimum dimensions for a full-size automobile space as required by Arlington County standards [Section 14.3.3.I.1].

Application and Compliance

When applying for an accessory dwelling permit in Arlington County, the applicant must include evidence of the creation of any required additional parking spaces [Section 12.9.2.B.3]. Additionally, the application must be accompanied by a floor plan of the ADU and a certified plat of the lot [Section 12.9.2.B].

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