722.3.2 Concrete Masonry Walls
|TYPE OF AGGREGATE||FIRE-RESISTANCE RATING (hours)|
|Pumice or expanded slag||1.5||1.9||2.1||2.5||2.7||3.0||3.2||3.4||3.6||3.8||4.0||4.2||4.4||4.5||4.7|
|Expanded shale, clay or slate||1.8||2.2||2.6||2.9||3.3||3.4||3.6||3.8||4.0||4.2||4.4||4.6||4.8||4.9||5.1|
|Limestone, cinders or unexpanded slag||1.9||2.3||2.7||3.1||3.4||3.7||4.0||4.3||4.5||4.8||5.0||5.2||5.5||5.7||5.9|
|Calcareous or siliceous gravel||2.0||2.4||2.8||3.2||3.6||3.9||4.2||4.5||4.8||5.0||5.3||5.5||5.8||6.0||6.2|
- Values between those shown in the table can be determined by direct interpolation.
- 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.
- Requirements of ASTM C55, ASTM C73, ASTM C90 or ASTM C744 shall apply.
- 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.
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 of the wall to be the fire-exposed side. The fire-resistance rating of the wall shall not exceed the lower of the two values calculated.
Installation of finishes shall be as follows:
- Gypsum wallboard and gypsum lath applied to concrete masonry or concrete walls shall be secured to wood or steel furring members spaced not more than 16 inches (406 mm) on center (o.c.).
- Gypsum wallboard shall be installed with the long dimension parallel to the furring members and shall have all joints finished.
- Other aspects of the installation of finishes shall comply with the applicable provisions of Chapters 7 and 25.