What would everyone use around Class A pipe to seal it around the opening in the cinder block wall we put an 8" hole in? The pipe is snug but there's a few gaps here and there. What do you suggest I seal it with? Contractor said Firestop foam...... Don't think that's correct...?
No, it's actually Metal Fab Class A Temp Guard pipe, 6" inner stainless steel flue with 9" exterior diameter, so the hole is actually 9" plus some change... 1.5" clearances to combustibles. Mortar is what I'm going to use I think.
Don't use regular great stuff. They sell 3M fireblock foam that is used to seal between penetrations in newer firecode applications - plumbing and wire pulls. I've used it to seal gaps in CO2 protected compartments at work that exceed 350-400F. If the gap isn't large high temp silicone would work, or just buy mortar in the caulking tube
How about fire stop caulk, how big is your gap. I believe the 3M firestop caulk is rated to 2000 degrees? If its bigger than caulk can fix I'd suggest hydraulic cement or mortar mix... Btw, I'm a contractor with 25 yrs experience.
I'd use the 3M caulk, they have it at HD and Lowes.... I'm not a fan of foam, it's a pain to remove when the time comes and it can be a sloppy mess.
IMO Furnace cement is better suited for stove repairs, metal to metal. This situation should use something more flexible, the furnace cement will crack and blow out when the metal expands and moves while the block does not.
I with Justwood on this one. However, I think bobdog2o02 is also correct and the 3M material will work as wells.
Fire caulk is the easiest and quickest. Fire foam is a mess and harder to control. Works but more of a quick and dirty application to pass inspections. It is used all the time on my commercial jobs. But it is limited on the sized of the hole or gap which does not affect your small one. Big gaps and holes require fire x drywall and tapped and mudded. Mortar is good too but a bit more time consuming and slightly messy but would look the best if you can see your penetration. You have many suggestions above and all will work except the regular foam. I wouldn't use that. So basically it's up to you and what you feel like doing but I'd narrow it down to the fire caulk or mortar. Just me. Good Luck!
