FIRE RATINGS OF CONCRETE MASONRY WALLS

TABLE 3:
FIRE RATINGS OF CONCRETE MASONRY WALLS
LIMESTONE, CINDERS OR AIR-COOLED SLAG AGGREGATES

medium weight block

Wight (W)		Fire Resistance Rating
nominal	specified	partial grouted or hollow masonry	solid grouted masonry
4" 6" 8" 8" special 10" 12"	3 5/8" 5 5/8" 7 5/8" 7 5/8" 9 5/8" 11 5/8"	less than 1 hour 1 hour 1 hour 3 hour 2 hour 3 hour	1 hour 3 hour 4 hour 4 hour 4 hour 4 hour

TABLE 4:
FIRE RATINGS OF CONCRETE MASONRY WALLS
CALCAREOUS OR SILICEOUS AGGREGATES

normal weight block

Wight (W)		Fire Resistance Rating
nominal	specified	partial grouted or hollow masonry	solid grouted masonry
4" 6" 8" 8" special 10" 12"	3 5/8" 5 5/8" 7 5/8" 7 5/8" 9 5/8" 11 5/8"	less than 1 hour 1 hour 1 hour 2 hour 2 hour 2 hour	1 hour 3 hour 4 hour 4 hour 4 hour 4 hour

Excerpt from UNIFORM BUILDING CODE (1997 EDITION)
TABLE NO.7-B RATED FIRE-RESISTIVE PERIODS FOR VARIOUS WALLS AND PARTITIONS

Example
8"expanded shale block,
52% solid
Eq. Th. = .52 x 7.625" =4.05"
Fire resistance = 2hr (3.8 reg.)

Solid grout wall,
Th. = 7.625"
Fire resistance = 4 hr (plus)

Add 1/2" portland cement plaster
4.05" + .50" = 4.55"
Fire resistance = 2 hr
Add 1/2" gypsum plaster
4.05" + .75" =4.8"
Fire resistance = 3 hr

FOOTNOTES TO TABLE NO. 7-B

* Thickness shown for brick and clay tile are nominal thicknesses plastered in which case thicknesses are net. Thicknesses shown for solid or hollow concrete masonry units are "equivalent thicknesses" as defined in U.B.C. Standard No. 21-4. Thickness includes plaster, lath and gypsum wallboard where mentioned and grout when all cells are solidly grouted.

** See also Footnote 2. The equivalent thickness may include the thickness of portland cement plaster or 1.5 times the thickness of gypsum plaster applied in accordance with the requirements of Chapter 25 of the code.