International Building Code 502.1
Definitions. The followingwords and terms shall, for the
purposes of this chapter and as used elsewhere in this code,
have the meanings shown herein.
AREA, BUILDING. The area included within surrounding
exteriorwalls (or exteriorwalls and firewalls) exclusive of vent
shafts and courts. Areas of the building not provided with surrounding
walls shall be included in the building area if such
areas are included within the horizontal projection of the roof
or floor above.
BASEMENT. That portion of a building that is partly or completely
below grade plane (see “Story above grade plane” in
Section 202). A basement shall be considered as a story above
grade plane where the finished surface of the floor above the
basement is:
1. More than 6 feet (1829 mm) above grade plane; or
2. More than 12 feet (3658 mm) above the finished ground
level at any point.
EQUIPMENT PLATFORM. An unoccupied, elevated platform
used exclusively for mechanical systems or industrial
process equipment, including the associated elevated walkways,
stairs and ladders necessary to access the platform (see
Section 505.5).
GRADE PLANE. A reference plane representing the average
of finished ground level adjoining the building at exterior
walls. Where the finished ground level slopes away from the
exterior walls, the reference plane shall be established by the
lowest points within the area between the building and the lot
line or, where the lot line is more than 6 feet (1829 mm) from
the building, between the building and a point 6 feet (1829 mm)
from the building.
HEIGHT, BUILDING. The vertical distance from grade
plane to the average height of the highest roof surface.
HEIGHT, STORY. The vertical distance from top to top of
two successive finished floor surfaces; and, for the topmost
story, from the top of the floor finish to the top of the ceiling
joists or, where there is not a ceiling, to the top of the roof rafters.
MEZZANINE. An intermediate level or levels between the
floor and ceiling of any story and in accordance with Section
505.