International Building Code Section 601


International Building Code 601.1

Scope. The provisions of this chapter shall control the
classification of buildings as to type of construction.

International Building Code 602.1

General. Buildings and structures erected or to be
erected, altered or extended in height or area shall be classified
in one of the five construction types defined in Sections 602.2
through 602.5. The building elements shall have a fire-resistance
rating not less than that specified in Table 601 and exterior
walls shall have a fire-resistance rating not less than that
specified in Table 602.

Minimum requirements. A building or portion
thereof shall not be required to conform to the details of a
type of construction higher than that type, which meets the
minimum requirements based on occupancy even though
certain features of such a building actually conform to a
higher type of construction.

International Building Code 602.1.1

Minimum requirements. A building or portion
thereof shall not be required to conform to the details of a
type of construction higher than that type, which meets the
minimum requirements based on occupancy even though
certain features of such a building actually conform to a
higher type of construction.

International Building Code 602.2

Types I and II. Type I and II construction are those types
of construction in which the building elements listed in Table
601 are of noncombustible materials, except as permitted in
Section 603 and elsewhere in this code.

International Building Code 602.3

Type III. Type III construction is that type of construction
in which the exterior walls are of noncombustible materials
and the interior building elements are of any material
permitted by this code. Fire-retardant-treated wood framing
complying with Section 2303.2 shall be permitted within exterior
wall assemblies of a 2-hour rating or less.

International Building Code 602.4

Type IV. Type IV construction (Heavy Timber, HT) is
that type of construction in which the exterior walls are of
noncombustible materials and the interior building elements
are of solid or laminated wood without concealed spaces. The
details of Type IV construction shall comply with the provisions
of this section. Fire-retardant-treatedwood framing complying
with Section 2303.2 shall be permitted within exterior
wall assemblies with a 2-hour rating or less. Minimum solid
sawn nominal dimensions are required for structures built
using Type IV construction (HT). For glued-laminated members
the equivalent net finished width and depths corresponding
to the minimum nominal width and depths of solid sawn
lumber are required as specified in Table 602.4.

Columns. Wood columns shall be sawn or glued
laminated and shall not be less than 8 inches (203 mm),
nominal, in any dimension where supporting floor loads and
not less than 6 inches (152 mm) nominal in width and not
less than 8 inches (203 mm) nominal in depth where supporting
roof and ceiling loads only. Columns shall be continuous
or superimposed and connected in an approved
manner.

Floor framing.Wood beams and girders shall be of
sawn or glued-laminated timber and shall be not less than 6
inches (152 mm) nominal in width and not less than 10
inches (254 mm) nominal in depth. Framed sawn or
glued-laminated timber arches, which spring from the floor
line and support floor loads, shall be not less than 8 inches
(203 mm) nominal in any dimension. Framed timber trusses
supporting floor loads shall have members of not less than 8
inches (203 mm) nominal in any dimension.

Roof framing. Wood-frame or glued-laminated
arches for roof construction, which spring from the floor
line or from grade and do not support floor loads, shall have
members not less than 6 inches (152 mm) nominal in width
and have less than 8 inches (203 mm) nominal in depth for
the lower half of the height and not less than 6 inches (152
mm) nominal in depth for the upper half. Framed or gluedlaminated
arches for roof construction that spring from the
top of walls or wall abutments, framed timber trusses and
other roof framing, which do not support floor loads, shall
have members not less than 4 inches (102 mm) nominal in
width and not less than 6 inches (152 mm) nominal in depth.
Spaced members shall be permitted to be composed of two
or more pieces not less than 3 inches (76 mm) nominal in
thickness where blocked solidly throughout their intervening
spaces or where spaces are tightly closed by a continuous
wood cover plate of not less than 2 inches (51 mm)
nominal in thickness secured to the underside of the members.
Splice plates shall be not less than 3 inches (76 mm)
nominal in thickness. Where protected by approved automatic
sprinklers under the roof deck, framing members
shall be not less than 3 inches (76 mm) nominal in width.

Floors. Floors shall be without concealed spaces.
Wood floors shall be of sawn or glued-laminated planks,
splined or tongue-and-groove, of not less than 3 inches (76
mm) nominal in thickness covered with 1-inch (25 mm)
nominal dimension tongue-and-groove flooring, laid crosswise
or diagonally, or 0.5-inch (12.7 mm) particleboard or
planks not less than 4 inches (102 mm) nominal in width set
on edge close together and well spiked and covered with
1-inch (25 mm) nominal dimension flooring or 15/32-inch
(12 mm) wood structural panel or 0.5-inch (12.7 mm)
particleboard. The lumber shall be laid so that no continuous
line of joints will occur except at points of support.
Floors shall not extend closer than 0.5 inch (12.7 mm) to
walls. Such 0.5-inch (12.7 mm) space shall be covered by a
molding fastened to the wall and so arranged that it will not
obstruct the swelling or shrinkage movements of the floor.
Corbeling of masonry walls under the floor shall be permitted
to be used in place of molding.
602.4.5 Roofs. Roofs shall be without concealed spaces and
wood roof decks shall be sawn or glued laminated, splined
or tongue-and-groove plank, not less than 2 inches (51 mm)
nominal in thickness, 11/8-inch-thick (32 mm) wood struc-

tural panel (exterior glue), or of planks not less than 3 inches
(76 mm) nominal in width, set on edge close together and
laid as required for floors. Other types of decking shall be
permitted to be used if providing equivalent fire resistance
and structural properties.

Roofs. Roofs shall be without concealed spaces and
wood roof decks shall be sawn or glued laminated, splined
or tongue-and-groove plank, not less than 2 inches (51 mm)
nominal in thickness, 11/8-inch-thick (32 mm) wood struc-
tural panel (exterior glue), or of planks not less than 3 inches
(76 mm) nominal in width, set on edge close together and
laid as required for floors. Other types of decking shall be
permitted to be used if providing equivalent fire resistance
and structural properties.

Partitions. Partitions shall be of solid wood construction
formed by not less than two layers of 1-inch (25
mm) matched boards or laminated construction 4 inches
(102 mm) thick, or of 1-hour fire-resistance-rated construction.

Exterior structural members. Where a horizontal
separation of 20 feet (6096 mm) or more is provided, wood
columns and arches conforming to heavy timber sizes shall
be permitted to be used externally.

International Building Code 602.4.1

Columns. Wood columns shall be sawn or glued
laminated and shall not be less than 8 inches (203 mm),
nominal, in any dimension where supporting floor loads and
not less than 6 inches (152 mm) nominal in width and not
less than 8 inches (203 mm) nominal in depth where supporting
roof and ceiling loads only. Columns shall be continuous
or superimposed and connected in an approved
manner.

International Building Code 602.4.2

Floor framing.Wood beams and girders shall be of
sawn or glued-laminated timber and shall be not less than 6
inches (152 mm) nominal in width and not less than 10
inches (254 mm) nominal in depth. Framed sawn or
glued-laminated timber arches, which spring from the floor
line and support floor loads, shall be not less than 8 inches
(203 mm) nominal in any dimension. Framed timber trusses
supporting floor loads shall have members of not less than 8
inches (203 mm) nominal in any dimension.

International Building Code 602.4.3

Roof framing. Wood-frame or glued-laminated
arches for roof construction, which spring from the floor
line or from grade and do not support floor loads, shall have
members not less than 6 inches (152 mm) nominal in width
and have less than 8 inches (203 mm) nominal in depth for
the lower half of the height and not less than 6 inches (152
mm) nominal in depth for the upper half. Framed or gluedlaminated
arches for roof construction that spring from the
top of walls or wall abutments, framed timber trusses and
other roof framing, which do not support floor loads, shall
have members not less than 4 inches (102 mm) nominal in
width and not less than 6 inches (152 mm) nominal in depth.
Spaced members shall be permitted to be composed of two
or more pieces not less than 3 inches (76 mm) nominal in
thickness where blocked solidly throughout their intervening
spaces or where spaces are tightly closed by a continuous
wood cover plate of not less than 2 inches (51 mm)
nominal in thickness secured to the underside of the members.
Splice plates shall be not less than 3 inches (76 mm)
nominal in thickness. Where protected by approved automatic
sprinklers under the roof deck, framing members
shall be not less than 3 inches (76 mm) nominal in width.

International Building Code 602.4.4

Floors. Floors shall be without concealed spaces.
Wood floors shall be of sawn or glued-laminated planks,
splined or tongue-and-groove, of not less than 3 inches (76
mm) nominal in thickness covered with 1-inch (25 mm)
nominal dimension tongue-and-groove flooring, laid crosswise
or diagonally, or 0.5-inch (12.7 mm) particleboard or
planks not less than 4 inches (102 mm) nominal in width set
on edge close together and well spiked and covered with
1-inch (25 mm) nominal dimension flooring or 15/32-inch
(12 mm) wood structural panel or 0.5-inch (12.7 mm)
particleboard. The lumber shall be laid so that no continuous
line of joints will occur except at points of support.
Floors shall not extend closer than 0.5 inch (12.7 mm) to
walls. Such 0.5-inch (12.7 mm) space shall be covered by a
molding fastened to the wall and so arranged that it will not
obstruct the swelling or shrinkage movements of the floor.
Corbeling of masonry walls under the floor shall be permitted
to be used in place of molding.
602.4.5 Roofs. Roofs shall be without concealed spaces and
wood roof decks shall be sawn or glued laminated, splined
or tongue-and-groove plank, not less than 2 inches (51 mm)
nominal in thickness, 11/8-inch-thick (32 mm) wood struc-
tural panel (exterior glue), or of planks not less than 3 inches
(76 mm) nominal in width, set on edge close together and
laid as required for floors. Other types of decking shall be
permitted to be used if providing equivalent fire resistance
and structural properties.

International Building Code 602.4.5

Roofs. Roofs shall be without concealed spaces and
wood roof decks shall be sawn or glued laminated, splined
or tongue-and-groove plank, not less than 2 inches (51 mm)
nominal in thickness, 11/8-inch-thick (32 mm) wood struc-
tural panel (exterior glue), or of planks not less than 3 inches
(76 mm) nominal in width, set on edge close together and
laid as required for floors. Other types of decking shall be
permitted to be used if providing equivalent fire resistance
and structural properties.

International Building Code 602.4.6

Partitions. Partitions shall be of solid wood construction
formed by not less than two layers of 1-inch (25
mm) matched boards or laminated construction 4 inches
(102 mm) thick, or of 1-hour fire-resistance-rated construction.

International Building Code 602.4.7

Exterior structural members. Where a horizontal
separation of 20 feet (6096 mm) or more is provided, wood
columns and arches conforming to heavy timber sizes shall
be permitted to be used externally.

International Building Code 602.5

Type V. Type V construction is that type of construction
in which the structural elements, exterior walls and interior
walls are of any materials permitted by this code.