The usable area in an office building is the floor area available for
the tenant's use within his demised space. In general, it is measured from
the glass line of the exterior wall to the centerline of demising partitions.
The floor area occupied by structural elements (columns) within the space
is included in the usable area.
BOMA (Building Owners and Managers Association) has established standards
for calculating usable and rentable areas. The calculations should be standard
from building to building. However, the geometry of the space will effect
the amount of usable space required to accommodate a program of requirements.
Column spacing, size and shape of the space are the three most significant
influences on the plan efficiency of a space. In some situations, the perimeter
required to provide private offices with exterior windows in combination
with the depth of the office (corridor to exterior wall) may determine the
required usable area.