If you see water stains on your ceiling near or above a fireplace, and you know your roof isn’t damaged, you may need to inspect your chimney flashing. Notorious for leaking, chimneys let water into your home in a variety of ways, the most common of which is through the metal flashings.
What is Chimney Flashing?
Flashings are the strips of metal that are placed along the front edge, corners and ridges of your roof and around your chimney and skylights. They are meant to create a watertight seal where your chimney and roof intersect. But, if the flashing was not installed properly, if it is subjected to a violent storm, or its sealant has deteriorated, it can start to pull away from your roofing material and lead to water leaks.
How to Detect a Chimney Flashing Leak
One way to verify that the culprit is the chimney flashing is by running a low pressure hose around the chimney and roof intersection and check for water inside. This can be done with two people — one operating the hose and the other in the attic, with both people using cell phones or walkie-talkies. If you see any water inside, you need to get the flashing repaired. As always, exercise extreme caution when on a ladder and on your roof.
When to Replace Chimney Flashing
Ideally, you should have your chimney flashing inspected every 6 months. This helps prevent leaks from wreaking too much havoc inside your home. If your flashing is missing, rusted, visibly separated from the chimney, or completely covered with roofing tar (a quick stop-gap measure that may be covering up a larger problem), you should have it replaced. Also, any time you replace your roof’s shingles, you should have new flashing installed, so that it lasts as long as the new roof.
How to Repair Loose Chimney Flashing
If you think that the only problem with your flashing is that the sealant needs to be replaced, you can try to caulk it yourself. Here are some tips:
- First, remove leaves or other debris that may have accumulated in the gap between the flashing and chimney.
- Scrape away leftover hardened roofing cement with a chisel.
- Apply a generous amount of roofing cement behind the flashing.
- Attach the flashing tight against the chimney with masonry nails or screws.
- Cover all exposed nail or screw heads with roofing cement.
- Apply roofing cement to the joint between the flashing and brick.
- Smooth the roofing cement over that joint with a paint stirrer or putty knife.
Leaks around flashing can be particularly difficult to find and repair. Just one small opening in a corner can allow a significant amount of water inside, especially during a hard rain. If you have resealed the flashing and the roof still leaks, ask a roofing contractor to inspect your roof and repair the flashing. Roofing contractors with specific credentials in sheet metal work can repair and replace your flashing properly. They are also trained to spot the tiniest breaches in your chimney flashing and can save you hours of risky work on a ladder.