If an existing masonry wall is determined to have a fire rating less than that required (Refer to FAQ “How does one determine the fire resistance rating of an existing, single wythe, hollow concrete masonry wall?”), one option is to add wall finishes on one or both exposed surfaces to improve its fire resistance.
The following finishes add to the wall’s fire resistance rating, whether applied to one surface only or to both surfaces, when installed in compliance with ACI 216.1/TMS-0216 Section 5.3 or IBC Section 7184.108.40.206.
- Portland cement-sand plaster
- gypsum-sand plaster
- gypsum-vermiculite or perlite plaster
- gypsum wallboard
The fire-resistance contribution(s) of the finish(es) is(are) calculated in accordance with IBC Sections 7220.127.116.11 through 718.104.22.168 or ACI 216.1/TMS-0216 Section 5.2. For each finish type and thickness, two sets of calculations of finished wall fire resistance must be made: the first calculation set assumes that the finish is on the non-fire-exposed side and the second calculation set assumes that the finish is on the fire-exposed side. The smallest of the values calculated is the finished wall’s fire-resistance rating.
For a concrete masonry wall with a finish that contributes to the fire-resistance rating, the masonry alone is required to provide not less than one-half the total required fire resistance. Also, the contribution of the finish on the non-fire-exposed side of the wall cannot exceed one-half of the masonry’s contribution alone.
- Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies, ACI 216.1-07/TMS 0216-07
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