In the Event of a Chimney Leak, Check the Flashing
Moisture in a chimney system can be a costly problem and has various causes. One of the most common reasons for leakage that we come across on service calls is faulty flashing. The connection between the roof and the chimney is made watertight by flashing, but there always comes a time when the flashing must be repaired or replaced. To possibly avoid the hassle and expense of replacing rotten wood and making repairs for other kinds of structural damage, it’s best to get an annual chimney inspection, in which the flashing and all other parts of a chimney are closely inspected.
Flashing is apparently a challenge to install for some builders because we often discover that leakage is caused by improper installation, sometimes following the addition of a new roof.
The best universal method for installing flashing involves two metal panel parts. Builders in different regions choose different types of metal for flashing, and cost is also a deciding factor. In the south, aluminum and galvanized steel are the typical choices, though copper is used on high-end installations. Copper is actually the best material to use for flashing. Not only is copper durable, but it can be soldered to form a more watertight connection. In the Northeast, masons often use lead flashing because it’s a soft metal that is bent to shape easily. The type of material used isn’t as important as competent installation, in which a watertight connection is formed between the roof and the chimney.
First is the base or step flashing, which is installed underneath shingles and bends upward against the brick chimney. We frequently find holes and cracks when inspecting the L-shaped base flashing panels.
The counterflashing is the next part of the installation process. This metal piece bends down over the base flashing and is embedded into chimney mortar joints at the top to seal off or cap the top part of the base flashing.
Corners are often the most vulnerable parts of flashing. Even the highest quality work usually ends up with a small area to which urethane caulking must be applied, to ensure the completion of the waterproofing process.
When leakage occurs due to damaged flashing, there are times when additional caulking will resolve the problem. There are also plenty of times when there isn’t adequate overlapping of the flashing material, and more is required to repair it.
It’s not usually immediately detected, when there is a leak due to faulty flashing. Roof damage, wood rot, attic damage, and ceiling damage can all occur before homeowners are aware there is a problem. A great preventative measure besides annual chimney sweep inspections is to periodically check the chimney area from the attic for signs of leakage.
In conjunction with the flashing, a diversion roof called a “cricket” is often built to help ensure that a chimney is waterproof. A cricket is built behind the chimney at the roofline. Its triangular shape is especially helpful on steep roofs in which the chimney would otherwise be deluged with water when it rains.
Faulty flashing, as mentioned before, is just one of many potential causes of leakage in a chimney system. If you have any questions or would like help with your chimney and venting systems, call us at your earliest convenience.
Northeastern Chimney, Inc
37 Cody Street, West Hartford, CT 06110