722.3.2 Concrete masonry walls.
BC § 722.3.2
The fire-resistance rating of walls and partitions constructed of concrete masonry units shall be determined from Table 722.3.2. The rating shall be based on the equivalent thickness of the masonry and type of aggregate used. Table 722.3.2Minimum Equivalent Thickness (inches) of Bearing or Nonbearing Concrete Masonry Walls a, b, c, d Type of Aggregate Fire-Resistance Rating (hours) 1/23/411 1/41 1/21 3/422 1/42 1/22 3/433 1/43 1/23 3/44 Pumice or expanded slag1.51.92.12.52.73.03.23.43.63.84.04.24.44.54.7Expanded shale, clay or slate1.82.22.62.93.33.43.63.84.04.24.44.64.84.95.1Limestone, cinders or unexpanded slag1.92.32.73.13.43.74.04.34.54.85.05.25.55.75.9Calcareous or siliceous gravel2.02.42.83.23.63.94.24.54.85.05.35.55.86.06.2 For SI: 1 inch = 25.4 mm. a. Values between those shown in the table can be determined by direct interpolation. b. Where combustible members are framed into 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 in the table. c. Requirements of ASTM C 55, ASTM C 73, ASTM C 90 or ASTM C 744 shall apply. d. Minimum required equivalent thickness corresponding to the hourly fire-resistance rating for units with a combination of aggregate shall be determined by linear interpolation based on the percent by volume of each aggregate used in manufacture.
