We've got a brick chimney that's ~25 years old and it's got a quite a few cracks in the mortar (some hairline, some as thick is a quarter).

What's the best way to seal all those cracks? I assume mortar, but is there a specific type?

I'm not concerned so much with how it looks (can't really see it from the street), but we've had a slew of leaks coming in from all these cracks, so just need something that does a good job of sealing it long term.

1 Answer 1


Sure sounds like your chimney is a good candidate for a re pointing job. This involves removing all loose and damaged mortar, then pointing all the joints with a portland cement mortar. If you have never done this kind of work, read up on it. It can get quite involved if there are loose bricks etc. It may be a good idea to get a pro, so it will last awhile and not just fall out as soon as it dries. An alternative product for a quick temp fix can be found in a caulking tube. There are several products designed specifically for masonry and do a pretty good job in sealing small cracks. Remove as much loose mortar as you can to assure the masonry caulk sticks well.

  • Note that only a fire rated caulk should be used on a chimney. Some caulk can ignite.
    – Bryce
    Mar 18, 2016 at 22:46

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