Fire Ratings For Concrete Masonry Units
Using Equivalent Thickness Method as permitted by the International Building Code (IBC)
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| FIRE RATINGS – HOURS | |||||||
|---|---|---|---|---|---|---|---|
| UNIT WIDTH | BLOCK TYPE | FACE SHELL |
% SOLID |
EQUIVALENT THICKNESS |
NORMAL WEIGHT CONCRETE (Siliceous Gravel) |
MEDIUM WEIGHT (105-125lb per cubic ft blended) |
LIGHT WEIGHT (Under 105lbs per cubic ft) (Expanded clay, shale or slate) |
| 4″ 4″ |
2 Core Regular Solid |
1.0″ Solid |
70% 100% |
2.5 3.6 |
3/4 1-1/2 |
3/4 1-1/2 |
3/4 1-1/2 |
| 6″ 6″ 6″ |
2 Core Regular 2 Core 75% Solid Solid |
1.06″ 2.0″ Solid |
56% 75% 100% |
3.1 4.2 5.6 |
1 2 3 |
1 2 3-3/4 |
1 2 4 |
| 8″ 8″ 8″ 8″ 8″ |
2 Core Regular 2 Core 58% Solid 2 Core 63% Solid 2 Core 75% Solid Solid |
1.25″ 1.5″ 1.5″ 2.25″ Solid |
53% 58% 62% 75% 100% |
4.0 4.4 4.7 5.7 7.6 |
1-1/2 2 2 3 4 |
2 2 2 3 4 |
2 2 3 4 4 |
| 10″ | 2 Core Regular | 1.25″ | 51% | 4.9 | 2 | 2 | 3 |
| 12″ 12″ |
2 Core Regular 2 Core 56% Solid |
1.5″ 2.125″ |
50% 50% |
5.8 6.5 |
3 4 |
3 4 |
4 4 |
Some of the above listed shapes are non-stock items. Please inquire
Note:
Increasing Fire Ratings: Walls composed of hollow concrete masonry units having a nominal thickness of 8 inches or greater and having a fire resistance rating of at least 2 hours shall be classified as 4 hours when the hollow spaces are completely filled with perlite or vermiculite, grout or a material such as expanded slag, clay shale, slate or sand.