Hot take: you don't always need to replace a cracked flue tile

I see so many guys in here saying any crack means a full reline, but that's not what the NFPA 211 code says for masonry chimneys. If the crack is under 1/8 inch and the tile is still fully supported, a proper sealant can be a code-compliant fix that saves the client a ton. When was the last time you actually measured the gap before giving the quote?

4 comments

4 Comments

the_jennifer2mo ago

But that dime trick @sage_green mentioned only checks the width, not the depth or length of the crack. A hairline can run the full height of the tile behind the glaze, which a sealant won't hold if the heat makes it shift. I've seen those "simple fixes" fail and let carbon monoxide sneak in, which isn't a risk worth taking to save some money.

sage_green2mo ago

Yeah, the "two second look" thing is way too real. I read a chimney sweep's blog a while back that said most hairline cracks are just in the glaze, not the actual clay. They pointed out that if you can't fit a dime in it and the tile isn't loose, sealing it is totally fine. Saves everyone a huge headache and a bigger bill.

fiona_west212mo agoTop Commenter

Honestly used to think every crack meant a full replacement, no question. Then my own guy showed me the dime trick on my fireplace last year. He sealed a hairline that looked scary, and it's been totally fine through a whole winter. Saved me like two grand right there. Now I get why the quick look feels lazy, but sometimes the fix really is that simple.

cora5182mo ago

Oh, you measured it? That's a new one. Usually the quote just appears by magic after a two second look up the chimney. I guess my tape measure's been in the truck this whole time for no reason.