Gross floor area

Gross floor area, brüt alan in Turkish, is the size of a space or building measured including the area taken up by walls, columns and partitions. Roughly speaking, it is measured to the outside face of the external walls. Unlike net area, it includes the unusable area inside the walls.

More than one kind of gross

People talk about “gross” as if it had a single meaning, but in practice there are several ways to calculate it. A flat measured with its own walls only gives one figure; add its share of common areas such as stairs, corridors and shelters, and you get another. In Turkey, sales contracts, floor area ratio calculations and cost estimates should state clearly which definition they use; the gap between two figures quoted for the same flat usually comes from here. The rules for measuring and calculating are set out in the relevant regulations and standards.

How it is used in projects

Architectural drawings give the gross area of each floor, the total construction area and the area of each unit in separate schedules. These schedules underpin cost estimates, permit fees and building inspection paperwork. A mismatch between the area schedule and the drawings is one of the most common errors in a project set, so the schedule should be updated with every revision. Pulling areas directly from a BIM model reduces that risk, provided the measuring rules are set up correctly in the model.