Code of Massachusetts Regulations › 780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS › Chapter 7 - Fire and Smoke Protection Features › Section 721 - CALCULATED FIRE RESISTANCE › Subsection 721.4 - Clay brick and tile masonry

Current through Register 1525, July 5, 2024
The provisions of this section contain procedures by which
				  the
fire-resistance ratings
of clay brick and tile masonry are
				  established by calculations.
721.4.1
Masonry walls.
The
fire-resistance rating
of
				masonry walls shall be based upon the equivalent thickness as calculated in
				accordance with this section. The calculation shall take into account finishes
				applied to the wall and airspaces between wythes in multiwythe construction.
TABLE 721.4.1(1) FIRE-RESISTANCE PERIODS OF CLAY
				  MASONRY WALLS
MATERIAL TYPE
MINIMUM REQUIRED EQUIVALENT THICKNESS FOR FIRE
							 RESISTANCEa, b, c (inches)
1 hour
2
							 hour
3 hour
4 hour
Solid brick of clay or
							 shaled
2.7
3.8
4.9
6.0
Hollow brick or tile of clay or shale,
							 unfilled
2.3
3.4
4.3
5.0
Hollow brick or tile of clay or shale, grouted or
							 filled with materials specified in Section 721.4.1.1.3
3.0
4.4
5.5
6.6
For SI: 1 inch = 25.4 mm.
a. Equivalent thickness as determined from Section
							 721.4.1.1.
b. Calculated fire resistance between the hourly
							 increments listed shall be determined by linear interpolation.
c. Where combustible members are framed in the wall,
							 the thickness of solid material between the end of each member and the opposite
							 face of the wall, or between members set in from opposite sides, shall not be
							 less than 93 percent of the thickness shown.
d. For units in which the net cross-sectional area
							 of cored brick in any plane parallel to the surface containing the cores is at
							 least 75 percent of the gross cross-sectional area measured in the same
							 plane.
TABLE 721.4.1(2) FIRE-RESISTANCE RATINGS FOR BEARING
				  STEEL FRAME BRICK VENEER WALLS OR PARTITIONS
WALL OR PARTITION ASSEMBLY
PLASTER SIDE
EXPOSED (hours)
BRICK
							 FACED SIDE
EXPOSED (hours)
Outside facing of steel studs:
							 1/2" wood fiberboard
							 sheathing next to studs,3/4"
							 airspace formed with 3/4" *
							 15/8" wood strips placed over
							 the fiberboard and secured to the studs;
metal or wire lath nailed
							 to such strips, 33/4" brick
							 veneer held in place by filling
							 3/4" airspace between the
							 brick and lath with mortar. Inside facing of
							 studs:3/4"unsanded gypsum
							 plaster on metal or wire lath attached
							 to5/16" wood strips secured
							 to edges of the studs.
1.5
4
Outside facing of steel studs:. 1" insulation board
							 sheathing attached to studs, 1" airspace, and
							 33/4" brick veneer attached
							 to steel frame with metal ties every 5th course. Inside facing of
							 studs:7/8" sanded gypsum
							 plaster (1:2 mix) applied on metal or wire lath attached directly to the
							 studs.
1.5
4
Same as above except use
							 7/8" vermiculite-gypsum
							 plaster or 1" sanded gypsum plaster (1:2 mix) applied to metal or
							 wire.
2
4
Outside facing of steel studs:
							 1/2" gypsum sheathing board,
							 attached to studs, and 33/4"
							 brick veneer attached to steel frame with metal ties every 5th course. Inside
							 facing of studs:1/2" sanded
							 gypsum plaster (1:2 mix) applied to
							 1/2" perforated gypsum lath
							 securely attached to studs and having strips of metal lath 3 inches wide
							 applied to all horizontal joints of gypsum lath.
2
4
For SI: 1 inch = 25.4 mm.
TABLE 721.4.1(3) VALUES OF
R
n
				  0.59
R
n0.59
R
(hours)
1
1.0
2
1.50
3
1.91
4
2.27
TABLE 721.4.1(4) COEFFICIENTS FOR PLASTER,
pl
a
THICKNESS OF PLASTER (inch)
ONE SIDE
TWO SIDE
1/2
0.3
0.6
5/8
0.37
0.75
3/4
0.45
0.90
For SI: 1 inch = 25.4 mm.
a. Values listed in table are for 1:3 sanded gypsum
							 plaster.
TABLE 721.4.1(5) REINFORCED MASONRY
				  LINTELS
NOMINAL LINTEL WIDTH
(inches)
MINIMUM LONGITUDINAL
							 REINFORCEMENT COVER FOR FIRE RESISTANCE (inch)
1 hour
2
							 hour
3 hour
4 hour
6
11/2
2
NP
NP
8
11/2
11/2
13/4
3
10 or more
11/2
11/2
11/2
13/4
For SI: 1 inch = 25.4 mm.
NP = Not permitted.
TABLE 721.4.1(6) REINFORCED CLAY MASONRY
				  COLUMNS
COLUMN SIZE
FIRE-RESISTANCE RATING (hour)
1
2
3
4
Minimum column dimension (inches)
8
10
12
14
For SI: 1 inch = 25.4 mm.
721.4.1.1
Equivalent thickness.
The
fire-resistance ratings
of walls or partitions constructed of solid or hollow clay masonry units shall
				be determined from Table 721.4.1(1) or 721.4.1(2). The equivalent thickness of
				the clay masonry unit shall be determined by Equation 7-8 when using Table
				721.4.1(1). The
fire-resistance rating
determined from Table
				721.4.1(1) shall be permitted to be used in the calculated
fire-resistance rating
procedure in Section 721.4.2.
T
e =
V
n
/LH
(Equation 7-8)
where:
T
e = The equivalent
				  thickness of the clay masonry unit (inches).
V
n = The net volume
				  of the clay masonry unit (inch3).
L
= The specified length of the clay masonry
				  unit (inches).
H
= The specified height of the clay masonry
				  unit (inches).
721.4.1.1.1
Hollow
				clay units.
The equivalent thickness,
T
e, shall be the value obtained for
				hollow clay units as determined in accordance with Equation 7-8. The net
				volume,
V
n, of the units shall be
				determined using the gross volume and percentage of void area determined in
				accordance with ASTM C 67.
721.4.1.1.2
Solid grouted clay
				units.
The equivalent thickness of solid grouted clay masonry units
				shall be taken as the actual thickness of the units.
721.4.1.1.3
Units with filled
				cores.
The equivalent thickness of the hollow clay masonry units is the
				actual thickness of the unit when completely filled with loose-fill materials
				of: sand, pea gravel, crushed stone, or slag that meet ASTM C 33 requirements;
				pumice, scoria, expanded shale, expanded clay, expanded slate, expanded slag,
				expanded fly ash, or cinders in compliance with ASTM C 331; or perlite or
				vermiculite meeting the requirements of ASTM C 549 and ASTM C 516,
				respectively.