The TOP 5 Sources of Chimney Leaks
#1 Rain Going Straight In from the Top
A chimney cover makes sense to most people. Not only does it keep the rain out, but keeps birds, animals, and debris out
#2 Leaks from Cracks in the Chimney Crown
The chimney crown is the cement part on top of the chimney – some chimneys have crowns, some don’t. You can see that the very purpose of the chimney crown is to keep rain out. Cracks in the chimney crown can occur from shifting of the structure or from shrinkage dating back to the first day the crown was put on. When your crown has cracks, the water goes right through those cracks.
How to fix a cracked crown depends upon how bad the damage is. Most crowns have small cracks. Even small ones need to be fixed because all big cracks started out as small ones. Water freezes and thaws in the cracks all winter long, year after year, forcing small cracks to eventually become big cracks.
Once chimney crown damage is significant, though, the only fix it is to remove and relay the masonry.
#3 Chimneys Leaking From the Inside Out from Condensation
Gas fumes are very low temperature and have a lot of moisture in them. Sometimes these fumes were condense on the inside of this chimneys, literally soaking the bricks and keeping them moist all the time.
#4 Chimney Flashing Causes Leaks
The flashing is what keeps water from going into the place where the brick structure comes through the roof (or otherwise comes close to the roof.) There’s a fairly large gap between the bricks and the roof and water will pour through that hole if it’s not sealed up. Flashing is often aluminum that goes in between a couple of bricks and bends to go on top of the shingles. Some sort of waterproof “stuff” seals those spots. Though it’s far from the best choice, the “stuff” is often tar.
In any event, flashing doesn’t last forever and the tar lasts even less time.