We've purchased an older house built in the 70's, and one of the two chimney's lacks a fire break, meaning that you can see direct from the basement up into the second floor. There's a gap of approximately an inch between the flooring and the chimney, and when we had our chimneys capped the contractor recommended a fire break or fire stop but wasn't able to install it at the time.

My question is whether this is something I need a chimney professional to install or something that I can handle myself. He mentioned a part, unspecified, that was $25 or so, and I'm not sure what that is or where to start.

Any suggestions?

  • What kind of chimney do you have?
    – bcworkz
    Commented Jul 12, 2013 at 23:57
  • This one's a cinderblock chimney.
    – sogrady
    Commented Jul 15, 2013 at 15:16

1 Answer 1


Prefabricated chimneys have specific firestop spacers that must be used to maintain the terms of their listing, though they are often just sheet metal with a hole cut in it.

For constructed chimneys such as those like yours of masonry units, use firestop foam to fill the gap between framing and the masonry at every floor and ceiling level. This stuff is made by many of the same companies that make other materials used in construction. It's typically much like expanding polyurethane foam used as a sealant to fill gaps in construction, except it contains chemicals so the material will not support a flame, the stuff just chars. Regular foam will support a flame and puts off noxious fumes when burning.

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