Gross Floor Area (GFA) is measured from the exterior faces of exterior walls and from the center line of walls separating two buildings.
Non-residential floor area shall be the total GFA of a building not dedicated to one of the following uses:
- Community-based institutional facility;
- Emergency shelter;
- Lodging use with less than 30 rooms;
- Guest rooms and service areas of a lodging use with 30 or more rooms; or
- Education uses that are operated or chartered by the District government.
The GFA of a lodging use dedicated to function rooms, exhibit space, commercial adjuncts and any other use not considered guest room or service area shall be considered non-residential floor area.
For a building entirely detached from any other building, calculation of GFA for the portion of a story located partially below finished grade shall be as follows:
- Measure the portions of the perimeter of the story located partially below finished grade that have a height greater than or equal to four feet, when measured between the finished grade and the ground floor of the story above;
- Measure the total perimeter of the story located partially below finished grade;
- Divide the distance of the result of paragraph (1) by the distance of the result of paragraph (2); and
- Multiply this result by the total floor area of the story located partially below finished grade.
For a building attached at any point to a neighboring building, GFA of the portion of a story located partially below finished grade shall be calculated as follows:
- Establish a line between the midpoint of a building façade facing the nearest street at finished grade and the midpoint of the opposite building façade at finished grade;
- Determine the portion of this line where the distance between it, and the ground floor of the story directly above, is greater than or equal to six feet;
- Project a perpendicular line from the point along the line described in paragraph to the exterior walls of the building; and
- Measure the floor area that is between the projected perpendicular line and the other portions of the story with a height greater than or equal to six feet, when measured from the perpendicular line to the ground floor of the story above.
For more information on the following topics, please see the corresponding referenced sections:
- Rules of Measurement for Gross Floor Area (GFA) – Subtitle B § 304