Fire Ratings
Split Face Fire Ratings
FIRE RESISTANCE RATINGS/MINIMUM REQUIRED EQUIVALENT INCHES
|
Aggregate Type in
The Concrete Masonry Unit |
Fire Resistance
|
||||||
|
0.5 Hr.
|
0.75 Hr.
|
1 Hr.
|
1.5 Hr.
|
2 Hr.
|
3 Hr.
|
4 Hr.
|
|
|
Calcareous or siliceous gravel
|
2.0 in.
|
2.4 in.
|
2.8 in.
|
3.6 in.
|
4.2 in.
|
5.3 in.
|
6.2 in.
|
|
Limestone, cinders or slag
|
1.9 in.
|
2.3 in.
|
2.7 in.
|
3.4 in.
|
4.0 in.
|
5.0 in.
|
5.9 in.
|
|
Expanded clay, shale or slate
|
1.8 in.
|
2.2 in.
|
2.6 in.
|
3.3 in.
|
3.6 in.
|
4.4 in.
|
5.1 in.
|
|
Expanded slag or pumice
|
1.5 in.
|
1.9 in.
|
2.1 in.
|
2.7 in.
|
3.2 in.
|
4.0 in.
|
4.7 in.
|
Calculating “Equivalent Thickness” is simply determining what the block thickness would be if the same amount of material contained in a hollow unit were re-molded without core holes.
EQUIVALENT THICKNESS OF CONCRETE MASONRY UNITS (IN INCHES)
|
Nominal Width
(Inches) |
Equivalent Thickness
|
||
|
Based on Typical
Hollow Units (1) |
Based on Percent Solid
|
||
|
(75% – semi-solid)
|
(100% – solid)
|
||
|
4
|
2.68 (73.8%)
|
2.72
|
3.625
|
|
6
|
3.09 (55.0%)
|
4.22
|
5.625
|
|
8
|
4.04 (53.0%)
|
5.72
|
7.625
|
|
10
|
4.98 (51.7%)
|
7.22
|
9.625
|
|
12
|
5.77 (49.6%)
|
8.72
|
11.625
|
CALCULATING ESTIMATED FIRE RESISTANCE EXAMPLE
|
An 8″ hollow masonry wall is constructed of expanded slag units reported to be 53%* solid. What is the estimated fire resistance of the wall? (modular units) Equivalent Thickness = % solid x depth From Table: 3 hr. Fire Resistance requires 4.0 inches *Percentage solid can be calculated from net area or net volume as determined by ASTM C140 “Methods of Testing Concrete Masonry Units”. |
(1) Information based on data published by the National Concrete Masonry Association in NCMA TEK 7-1A, available at www.trenwyth.com.
