The truth about sealing your brick chimney

[Alan]

I get asked all the time if a chimney needs a waterproof sealer to stop leaks. I think most sealers actually trap moisture inside the brick which causes it to flake off when it freezes. It is usually better to fix the crown or the flashing than to spray a chemical on the outside. Bricks need to breathe so the water can evaporate naturally after a storm. Have you ever used a sealer that actually worked or did it just cause more peeling?

 

[bigbuZZ]

I went to a job last month where the homeowner had painted their chimney with a thick waterproof coating to stop a leak. The moisture from the house got trapped behind that skin and literally turned the inside of the bricks into mush. I had to tear down the top six courses because the faces were just falling off in my hands. A good cap and solid lead flashing are the only real ways to keep a chimney dry for the long haul.

 

[Alan]

I went to a job last month where the homeowner had painted their chimney with a thick waterproof coating to stop a leak. The moisture from the house got trapped behind that skin and literally turned the inside of the bricks into mush. I had to tear down the top six courses because the faces were just falling off in my hands. A good cap and solid lead flashing are the only real ways to keep a chimney dry for the long haul.

Does your local code require a specific type of breathable sealer for new builds?

 

[z3u$096]

@Alan As long as the mortar joints are in good shape, a breathable repellent will give you the necessary rain protection you need without causing the flaking you’re worried about.

 

[Alan]

A

@Alan As long as the mortar joints are in good shape, a breathable repellent will give you the necessary rain protection you need without causing the flaking you’re worried about.

Agree with this. How long ago was it when you worked with one like it.