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Can the fire resistance rating of an existing, single wythe concrete masonry wall be improved by adding wall finishes?


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 722.3.2.5.

  • 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 722.3.2.1 through 722.3.2.4 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.



The decision to utilize this information is not within the purview of the MIM, and persons making use of this information do so at their own risk. MIM makes no representation or warranties, expressed or implied, with respect to the accuracy or suitability of this information. MIM and its members disclaim liability for damages of any kind, including any special, indirect, incidental, or consequential damages, which may result from the use of this information. This information is not to be interpreted as indicating compliance with, or waiver of, any provision of any applicable building code, ordinance, standard or law.