This page provides guidelines for how gross floor area is calculated for special exception site plan projects and how requests to exclude from density calculations, spaces defined by the Zoning Ordinance as gross floor area, will be considered.
Relevant ACZO Citations
Article 3.1.1.C. of the Arlington County Zoning Ordinance (ACZO) defines gross floor area as follows:
Gross floor area is the sum of the area of the horizontal surface of the several floors of a building measured from the exterior faces of exterior walls, to include all floor area not defined as gross parking area.
Gross Parking Area is defined in Article 18.2 of the ACZO as:
The sum of the ground floor surface area actually used for parking spaces and the area of the horizontal surface of the floor(s) of a building, measured from the exterior faces of exteriors walls, devoted to off-street parking, loading and maneuvering space including all corridors, air shafts, elevators, stairwells and toilets incidental thereto, but not including area devoted to permitted and accessory uses other than parking and loading.
All areas meeting the definition of gross floor area, both above and below grade, count towards the calculation of floor area for density purposes. Further, pursuant to the Requirements of Administrative Regulation 4.1 (Section I of Final Site Plan Submittal Requirements) all such areas should be shown and accounted for as gross floor area on all plan drawings and application documents. If there are requests to exclude areas from the calculation of gross floor area, each area should be specifically identified in the site plan application. Additionally, the applicant must submit in the site plan application justification and rationale for each area requested to be excluded from calculation of gross floor area. All such requests for the exclusion of density of areas that do not meet the definition of gross parking area will be considered and acted on by the County Board. Finally, areas that support bike parking and storage are considered as meeting the Zoning Ordinance definition of Gross Parking Area.
While several approved site plan projects have included density exclusions for a variety of above- and below-grade spaces that do not meet the definition of gross parking area, these spaces still count towards gross floor area and requests to exclude these areas as density must be considered by the County Board. Examples of the types of spaces for which density exclusions have been requested and approved in the past include the following, however all future requests are to be evaluated on a case by case basis:
- Left-over spaces in the below-grade garage not used for, or ancillary to gross parking area that do not affect the bulk, mass, and height of the building (including but not limited to tenant storage, dog wash areas, bicycle repair rooms, etc.);
- Ancillary spaces below-grade used to store or provide for equipment, mechanical, engineering, and/or structural supports for the building;
- Vertical shafts that provide for venting through the building to the roof and eliminate vents on the building façade in support of the County’s goal of providing for better quality building design;
- Below-grade tenant fitness centers; and
- Below-grade offices (e.g, building manager or maintenance staff offices).
All of these spaces meet the ACZO definition of gross floor area and must be included in a project’s base density calculations. Site Plan applications must continue to provide the square footage for all building areas, both below and above grade, that meet the ACZO definition of gross floor area, including: core areas, elevator shafts, vents, mechanical rooms and closets, storage rooms, fire control rooms, above grade transformers, etc., on all floor plans.
Bicycle parking and storage areas are gross parking area in site plan projects. This is consistent with the Master Transportation Plan (MTP) Goals and Policies Summary and Bicycling Element, which recommend policies and implementation actions to support and encourage bicycle travel. These include providing secure, covered, and convenient bike parking as well as facilities to support bicycling (e.g., showers and lockers) in new development. Bicycle parking and storage includes areas for parking spaces, lockers, and accessory shower facilities.