Causes of leaking chimneys can usually be narrowed down to five reasons:

1. Rain Going Straight In from the Top of the Chimney

First and foremost, you should have a chimney cover.  Chimney covers not only keep the rain out, but also animals and debris.

1. Cracks in the Chimney Crown

The chimney crown is the cement part on top of the chimney. The bricks go up around the tile flue liners, but at the top you need something to stop the rain and snow from just falling in around the tiles. 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.

1. Leaks from the Inside Out due to Condensation

Condensation can occur in an unlined chimney.  Unlined chimneys are often found in older houses.  If the chimney is not lined, it will leak.

1. Chimney Flashing

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 is a fairly large gap between the bricks and the roof and water will pour through that hole if it’s not sealed up.

1. Leaking Bricks

Bricks and mortar both pass water.  The problem is the same as with the crown - the freezing and thawing all winter long with the resulting damage causing causes leaks in the house.

In today’s case, the shingles and step-flashing need replacing, along with some tuck pointing.  Tuck pointing restores the masonry mortar joints between the bricks and will provide a strong, water resistant joint that will extend the life of the masonry chimney.