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Infilling a CMU wall.

Question asked by on Dec 4, 2018

I have a question about infilling a CMU wall.  The existing 8” CMU wall was identified as a 1hour wall separating a gym and an indoor pool. The wall is existing and constructed in the 1970’s. I believe the wall construction to be consistent with UL No. U 907 which is a 3 hour wall assembly (but only 1-hour required). An opening approximately 8’-8” x 8’-0” was cut into the CMU wall to allow for equipment to be brought into the pool area. Due to the size of opening required, for the new and future pool equipment, the wall was infilled using 20ga galvanized metal studs and 5/8” Type X drywall to meet Gypsum Association detail GA 1072 for one hour wall. 

The opening infill was designed so that the equipment in the pool area could be taken out or brought in by removing this section or wall in the event of equipment replacement or maintenance. The integrity of the wall is maintained a the framed wall assembly is constructed tight to the masonry jambs of the opening. The jambs were filled with solid grout to ensure a solid edged. The joint at the drywall and cmu edge is sealed using UL approved fire caulking.


This opening is between two one story spaces, both A-3 occupancies. The one-hour rating of the wall was an existing condition to the original construction.


While we do not see a specific UL or tested assembly for a rated wall assembly that utilizes a combination of masonry wall and metal stud/drywall construction, we believe this to be a common practice, and with quality construction meets the intent of the code in maintaining a continuous wall.  Is my thinking correct on this?