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SECTION 602 CONSTRUCTION CLASSIFICATION

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.

TABLE 601 FIRE-RESISTANCE RATING REQUIREMENTS FOR BUILDING ELEMENTS (hours)


BUILDING ELEMENT
TYPE I
TYPE II
TYPE III
TYPE IV
TYPE V
A
B
Ae
B
Ae
B
HT
Ae
B
Structural framea
3b
2b
1
0
1
0
HT
1
0
Bearing walls
Exteriorg
3
2
1
0
2
2
2
1
0
Interior
3b
2b
1
0
1
0
1/HT
1
0
Nonbearing walls and partitions
Exterior
See Table 602
Nonbearing walls and partitions
Interiorf
0
0
0
0
0
0
See Section 602.4.6
0
0
Floor construction
Including supporting beams
and joists
2
2
1
0
1
0
HT
1
0
Roof construction
Including supporting beams
and joists
c
1c, d
1c, d
0d
1c, d
0d
HT
1c, d
0


For SI:    1 foot = 304.8 mm.

a.   The structural frame shall be considered to be the columns and the girders, beams, trusses and spandrels having direct connections to the columns and bracing members designed to carry gravity loads. The members of floor or roof panels which have no connection to the columns shall be considered secondary members and not a part of the structural frame.

b.   Roof supports: Fire-resistance ratings of structural frame and bearing walls are permitted to be reduced by 1 hour where supporting a roof only.

c1.  
 Except in high-rise buildings, Group A, E, F-1, H, I, L, M, R-1, R-2 and S-1 occupancies, fire protection of structural members shall not be required, including protection of roof framing and decking where every part of the roof construction is 20 feet or more above any floor immediately below. Fire-retardant-treated wood members shall be allowed to be used for such unprotected members.

c2.
   For high-rise buildings, Group A, E, I, L, R-1 and R-2 occupancies and other applications listed in Section 111 regulated by the Office of the State Fire Marshal, fire protection of members other than the structural frame shall not be required, including protection of roof framing and decking where every part of the roof construction is 20 feet or more above any floor immediately below.

c3
. One-story portions of Group A and E assembly occupancies the roof-framing system of Type II A or Type III A construction may be of unprotected construction when such roof-framing system is open to the assembly area and does not contain concealed spaces.

d.   In all occupancies, heavy timber shall be allowed where a 1-hour or less fire-resistance rating is required.

e.    An approved automatic sprinkler system in accordance with Section 903.3.1.1 shall be allowed to be substituted for 1-hour fire-resistance-rated construction, provided such system is not otherwise required by other provisions of the code or used for an allowable area increase in accordance with Section 506.3 or an allowable height increase in accordance with Section 504.2. The 1-hour substitution for the fire resistance of exterior walls shall not be permitted.

f.   Not less than the fire-resistance rating required by other sections of this code.

g.   Not less than the fire-resistance rating based on fire separation distance (see Table 602).

TABLE 602 FIRE-RESISTANCE RATING REQUIREMENTS FOR EXTERIOR WALLS BASED ON FIRE SEPARATION DISTANCEa,e


FIRE SEPARATION DISTANCE = X
(feet)
TYPE OF CONSTRUCTION
OCCUPANCY
GROUP H, L
OCCUPANCY
GROUP F-1, M, S-1
OCCUPANCY
GROUP A, B, E, F-2, I, R f, S-2, Ub,f

´ < 5c
All
3
2
1
5 £ ´ < 10
IA
3
2
1
Others
2
1
1
10 £ ´ < 30
IA, IB
2
1
1d
IIB, VB
1
0
0
Others
1
1
1d
X ³ 30
All
0
0
0


For SI:    1 foot = 304.8 mm.

a.    Load-bearing exterior walls shall also comply with the fire-resistance rating requirements of Table 601.

b.    For special requirements for Group U occupancies see Section 406.1.2

c.    See Section 705.1.1 for party walls.

d.    Open parking garages complying with Section 406 shall not be required to have a fire-resistance rating.

e.    The fire-resistance rating of an exterior wall is determined based upon the fire separation distance of the exterior wall and the story in which the wall is located.

f.    Group R-3, and Group U when used as accessory to Group R-3, shall not be required to have a fire-resistance rating where the fire separation distance is 5 feet or more.


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.

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.

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.

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-treated wood 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.

TABLE 602.4 WOOD MEMBER SIZE


MINIMUM NOMINAL SOLID SAWN SIZE
MINIMUM GLUED-LAMINATED NET SIZE
Width, inch
Depth, inch
Width, inch
Depth, inch
8
8
6¾
8¼
6
10
5
10½
6
8
5
8¼
6
6
5
6
4
6
3
67/8


For SI:    1 inch = 25.4 mm.
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.
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.
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 glued-laminated 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.
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 structural 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.
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.
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.
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.