Rentable area includes the usable area within
the office plus shared areas of the floor and building such as:
Shafts (vertical penetrations through floors) for mechanical systems,
elevators and stairs are excluded from rentable area calculations.
These spaces may equal between 10 and 20 percent of the area within the
leased office space.
BOMA (Building Owners and Managers Association) has established standards
for calculating usable and rentable areas. The calculations should be standard
from building to building.