Chimney Flashing Leaks

Chimney Flashing provides a Watertight Seal between the Chimney and Roof

By Mark J. Donovan

Chimney flashing is used to prevent roof leaks between where the chimney and the roof meet. If you have water spots on your ceiling near the chimney area most likely it is due to a chimney flashing leak. Chimney flashing leaks are quite common due to the fact that chimneys are not directly attached to the house frame.

Consequently if the chimney or house settles differently, which they inevitably do, the chimney flashing pulls away from the chimney and/or roof and signs of chimney flashing leaks begin to show up on your ceilings.

Chimney flashing leaks can also be associated with the type of chimney flashing used. Certain types of metal chimney flashing can rust and corrode. Even lead chimney flashing ages and becomes brittle and cracked over time.

Chimney flashing leaks can also occur if the cement and polyurethane caulk that seals the chimney flashing into the chimney brick mortar seams dries out and cracks. Water can seep into the cracks and work its way underneath the chimney flashing and eventually onto your ceilings.

The normal chimney flashing installation process involves applying metal step flashing up against the chimney and roof surface. Lead is commonly used for chimney flashing due to its ductile and solderability properties. Tin coated steel, galvanized steel and copper are also used for chimney flashing as they can be soldered, welded, or brazed as well.

Chimney Flashing provides a Watertight Seal between the Chimney and Roof

Chimney flashing should typically be replaced whenever the roof shingles are being replaced. There is no point in installing 25 year shingles on a roof and leaving 10 or 20 year old chimney flashing in place. If you want your entire roof to last for the next 25 years or so, replace the chimney flashing when re-shingling a roof.

Though a skilled do it yourself person can tackle installing chimney flashing it does involve some risk due to the fact that you are working on a roof. In addition, improper chimney flashing installation is unforgiving.

If the chimney flashing is installed incorrectly you’ll have water damage in your home after the first rain storm. Consequently, I would highly suggest calling in a professional and insured roofer if you believe you have a chimney flashing leak.

If you do decided to do your own chimney flashing installation make sure to wear proper rubber-soled shoes and clothing, and wear a harness to prevent falling from the roof.

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Also, make sure you have all of the right tools and materials handy so that you do not have to go up and down the ladder a half a dozen times. Frequent walking on the roofing shingles can damage the roof and increase your chances of falling.

For more help on Shingling Your Home’s Roof, see’s Asphalt Shingle Roofing Bid Sheet. The Asphalt Shingle Roofing Bid Sheet will help to ensure that your roof won’t end up with a blue tarp over it and a dumpster sitting in your yard for weeks as you wait for the roofing contractor to come back and finish roofing your home.

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