In an existing underground stairway, 3-hour fire separation is being requested, but there is an existing triangular floor penetration (with sides measuring 9", 7" and 6") where the stairway footprint changes, shown in the attached photograph. What would be the best product to provide a firestop? Hilti Firestop Block CFS-BL info indicates it is ideal for use in floors, but how is it adhered in a horizontal opening and what sealant is used around it?
Hi Steven - CFS-BL installed per UL Listed System C-AJ-0138 or mineral wool safing and FS-One Max installed per C-AJ-0090 would be good options for you here. I would recommend reaching out to your local rep to help with the installation guidance. If you don't know who your rep is, please give us a call at 1-800-879-8000 and our customer service team will be able to point you in the right direction.
Hope this helps!
Regards,
Nate Crawford - Lead FPE