Superlite | an Oldcastle Company

Technical Notes

Fire Resistance

Concrete block wall systems are unsurpassed in functioning as a barrier to contain the spread of fire. These systems effectively resist transmission of intense heat through the wall while also preventing the passage of flames and hot gases. The fire resistance rating period of concrete masonry elements is determined by testing, by calculation methods or through a listing service.

Equivalent Thickness
The equivalent thickness of a unit is the solid thickness that would be obtained if the same amount of concrete contained in a hollow unit was re-cast as a solid unit.

Loose fill Insulation
The fire resistive time period for concrete masonry units meeting the equivalent thickness required for a two-hour-fire-resistive rating in Item 3 (below) and having a thickness of not less than 7 5/8 inches is four hours when cores which are not grouted are filled with silicone-treated perlite loose-fill insulation; vermiculite loose-fill insulation; or expanded clay, shale or slate lightweight aggregate, sand or slag having a maximum particle size of 3/8 inches (Table No. 719.1(2)).

Blended Aggregates
The fire-resistance rating of concrete masonry units composed of a combination of aggregate types shall be based on equivalent thickness values determined as follows:
Tr = T1 x V1 + T2 x V2 .. = Tn x Vn
Tr = The minimum required equivalent thickness corresponding to the desired fire-resistance rating as listed in Table 719.1(2) for C.M.U. manufactured with a particular combination of aggregate types.
T1, T2,..Tn = The equivalent thickness for each aggregate Type 1,2,.n, respectively, used as indicated in Table 719.1(2) for the desired fire-resistance rating.
V1, V2,.. Vn = The percentage by volume of each aggregate Type 1, 2,.n, respectively, which is used in the manufacture of the C.M.U.

* More information about Fire Resistance can be found on our website Select the e-TEK Manual link from our home page, next select the Table of Contents, and finally select Section Seven titled Fire Resistance.

Fire Resistance