1724 N Spurgeon St, Unit A & C - Plan

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Table 2. Minimum equivalent thickness required (in.) for standard northwest block wall ratings. Cores can be filled with grout, loose- -33 (ref. 4) or C-331 (ref. 5) requirements. TEK NOTE June 2016 Concrete Masonry Fire Resistance Concrete masonry is a noncombustible construction material possessing excellent fire-resistive properties. The resistance of concrete masonry to fire is well established by extensive testing to be a function of the type of aggregate used in the manufacture of the masonry units and their equivalent thickness. The rated fire-resistive periods for block walls can be determined by knowing this information and complying with Table 721.1(2), item number 3 of the International Building Code (IBC)(ref. 1). This is an alternative code- recognized method to the Underwriters Laboratory (UL) listing service. The equivalent thickness of concrete masonry assemblies, TEA, shall be computed as the sum of the equivalent thickness (average solid thickness as shown in Figure 1) of the concrete masonry unit, TE, plus the equivalent thickness of finishes, TEF, per code equation 7 - 6. TEA = TE + TEF (Equation 7 - 6) TE = V/LH where: Concrete masonry units (CMU) are commonly manufactured with a combination or blend of aggregate types. The International Building Code covers this condition by reference to standard TMS 216 (ref. 6). The minimum equivalent thickness value required for a desired fire rating can be determined by interpolating between requirements for different aggregate types in proportion to the percentage by volume of each aggregate used in manufacture. For example, for a standard block manufactured in the Northwest, which is approximately a 60/40 percentage blend of gravel and pumice aggregates, the required equivalent thickness values to achieve various fire ratings are shown in Table 2. V= net volume of masonry unit, in.3 (per ASTM C-140)(ref. 2) L = specified length of masonry unit, in. H = specified height of masonry unit, in. Equivalent thickness values for concrete masonry units conforming to ASTM standard C-90 (ref 3) meeting minimum required faceshell and typical web dimensions are shown in Table 1. Individual block manufacturers may have higher values based on a greater solid percentage. Nominal Block Width (in.) Block Core Treatment Empty or Fill Cores Solid Fill 1 4 2.7 3.6 6 3.1 5.6 Fire Rating 1 Hr. 2 Hr. 3 Hr. 4 Hr. 2.52 3.80 4.78 5.60 Figure 1. Concrete masonry unit equivalent thickness TE = 0.53 (7.625) = 4.04 in. If this hollow unit is 53% solid, the equivalent thickness (TE) is 4.04 inches.