722.4 Clay Brick and Tile Masonry
The fire-resistance rating of masonry walls shall be based on 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.
MATERIAL TYPE | MINIMUM REQUIRED EQUIVALENT THICKNESS FOR FIRE RESISTANCE^{a, b, c} (inches) | |||
1 hour | 2 hours | 3 hours | 4 hours | |
Solid brick of clay or shale^{d} | 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 722.4.1.1.3 | 3.0 | 4.4 | 5.5 | 6.6 |
For SI: 1 inch = 25.4 mm.
- Equivalent thickness as determined from Section 722.4.1.1.
- Calculated fire resistance between the hourly increments listed shall be determined by linear interpolation.
- 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 be not less than 93 percent of the thickness shown.
- For units in which the net cross-sectional area of cored brick in any plane parallel to the surface containing the cores is not less than 75 percent of the gross cross-sectional area measured in the same plane.
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}" × 1^{5}/_{8}" wood strips placed over the fiberboard and secured to the studs; metal or wire lath nailed to such strips, 3^{3}/_{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 to ^{5}/_{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 3^{3}/_{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 previous assembly 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 3^{3}/_{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.
R_{n} 0.59 | R (hours) |
1 | 1.0 |
2 | 1.50 |
3 | 1.91 |
4 | 2.27 |
THICKNESS OF PLASTER (inch) | ONE SIDE | TWO SIDES |
^{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.
- Values listed in the table are for 1:3 sanded gypsum plaster.
NOMINAL LINTEL WIDTH (inches) | MINIMUM LONGITUDINAL REINFORCEMENT COVER FOR FIRE RESISTANCE (inches) | |||
1 hour | 2 hours | 3 hours | 4 hours | |
6 | 1^{1}/_{2} | 2 | NP | NP |
8 | 1^{1}/_{2} | 1^{1}/_{2} | 1^{3}/_{4} | 3 |
10 or more | 1^{1}/_{2} | 1^{1}/_{2} | 1^{1}/_{2} | 1^{3}/_{4} |
For SI: 1 inch = 25.4 mm.
NP = Not Permitted.
COLUMN SIZE | FIRE-RESISTANCE RATING (hours) |
|||
1 | 2 | 3 | 4 | |
Minimum column dimension (inches) | 8 | 10 | 12 | 14 |
For SI: 1 inch = 25.4 mm.
The fire-resistance ratings of walls or partitions constructed of solid or hollow clay masonry units shall be determined from Table 722.4.1(1) or 722.4.1(2). The equivalent thickness of the clay masonry unit shall be determined by Equation 7-8 where using Table 722.4.1(1). The fire-resistance rating determined from Table 722.4.1(1) shall be permitted to be used in the calculated fire-resistance rating procedure in Section 722.4.2.
(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).
Where plaster is applied to the wall, the total fire-resistance rating shall be determined by the formula:
(Equation 7-9)
where:
R = The fire-resistance rating of the assembly (hours).
R_{n} = The fire-resistance rating of the individual wall (hours).
pl = Coefficient for thickness of plaster.
Values for R_{n}^{0.59} for use in Equation 7-9 are given in Table 722.4.1(3). Coefficients for thickness of plaster shall be selected from Table 722.4.1(4) based on the actual thickness of plaster applied to the wall or partition and whether one or two sides of the wall are plastered.
Where a continuous airspace separates multiple wythes of the wall or partition, the total fire-resistance rating shall be determined by the formula:
(Equation 7-10)
where:
R = The fire-resistance rating of the assembly (hours).
R_{1}, R_{2} and R_{n} = The fire-resistance rating of the individual wythes (hours).
as = Coefficient for continuous airspace.
Values for R_{n}^{0.59} for use in Equation 7-10 are given in Table 722.4.1(3). The coefficient for each continuous airspace of ^{1}/_{2} inch to 3^{1}/_{2} inches (12.7 to 89 mm) separating two individual wythes shall be 0.3.
For a wall without finish on one side or having different types or thicknesses of finish on each side, the calculation procedures of this section shall be performed twice, assuming either side to be the fire-exposed side of the wall. The fire resistance of the wall shall not exceed the lower of the two values determined.
Exception: For exterior walls with a fire separation distance greater than 5 feet (1524 mm), the fire shall be assumed to occur on the interior side only.
The fire-resistance rating for walls or partitions consisting of two or more dissimilar wythes shall be permitted to be determined by the formula:
(Equation 7-11)
where:
R = The fire-resistance rating of the assembly (hours).
R1, R2 and Rn = The fire-resistance rating of the individual wythes (hours).
Values for R_{n}^{0.59} for use in Equation 7-11 are given in Table 722.4.1(3).