Concrete Masonry Fire Ratings A raging California fire consumed every wood-framed home in the vicinity. A masonry home is the lone survivor. The fire resistance ratings specified by building codes for masonry walls will vary with the type of building, its occupancy, and the fire zone in which the structure is located. The fire resistance rating of walls and partitions constructed of concrete masonry units shall be determined from Table 709.3.1 below. The rating shall be based on the equivalent thickness of the masonry and type of aggregate used.
Equivalent thickness is the average thickness of the solid material in the unit.
Determine the equivalent thickness in accordance with ASTM C 140. 2. Values between those shown in the table can be determined by direct interpolation. Requirements of ASTM C 55, C 73 or C 90 shall apply. These Units may vary with each manufacturer depending on the style of the block, mold configuration, and wear etc. 709.3.2 Filled Core Spaces.