Why is my chimney leaking after a new roof?
Short answer. A chimney that starts leaking after a new roof almost always has a flashing problem from the installation: old step or counterflashing that was reused, new flashing lapped the wrong way, counterflashing caulked onto the brick face instead of set into a mortar joint, or no cricket behind a wide chimney. Call the installer first, because a leak caused by how the roof was put on falls under the workmanship warranty.
The usual installation culprits
- Reused flashing. Bending old step flashing back into place saves time, but old metal has nail holes, rust and bends in the wrong spots. New shingles deserve new step flashing.
- Step flashing not woven. Each piece should sit under the shingle above it and over the one below. One long piece of L-shaped metal along the side of a chimney channels water under the shingles.
- Surface-mounted counterflashing. Counterflashing should be cut into a mortar joint and sealed. A strip glued or caulked to the brick face lets water run behind it once the caulk shrinks.
- No cricket. The residential code calls for a cricket, a small peaked diverter, on the uphill side of a chimney wider than 30 inches that does not meet the ridge. Without one, water and pine needles pile against the back.
- Nails through the flashing in the water path, often from a crew securing a loose piece the fast way.
Rule out the coincidence
Sometimes the timing is a coincidence. A cracked crown, a missing cap or porous brick can soak through during the first big rain after the job, and none of those are touched in a normal reroof. Water that appears inside the firebox or on the flue points to the top of the chimney. Water on the ceiling or attic framing beside the chimney points to the flashing.
What to do
- Photograph the stain and note the date, how hard it rained and the wind direction.
- Contact the installer in writing and ask for a hose test with someone watching in the attic.
- Ask for photos of the flashing they installed, and keep them with your warranty papers.
See chimney leaks and crickets, and roofing warranties explained for what a workmanship warranty should cover.