If you have a stain on the ceiling near your chimney, or water running down the chimney chase in the attic, you are in very common company. The chimney is one of the most frequent leak points on any roof. The reason is simple: it is a big hole through the roof, and the joint around it has to stay watertight through decades of weather while the roof and the masonry move at different rates.
How Chimney Flashing Is Supposed to Work
A properly flashed chimney is a layered system, not a bead of caulk.
Step Flashing
Individual L-shaped metal pieces woven into each course of shingles along the sides of the chimney. Each piece overlaps the one below so water sheds down and away.
Counter Flashing
Metal set into the mortar joints of the chimney and bent down over the step flashing. It covers the top edge so water cannot run behind it.
Front Apron
A single piece across the downhill face of the chimney, lapped over the shingles below.
Back Pan or Cricket
The uphill side takes the most water. A cricket is a small peaked structure that splits the flow around the chimney instead of letting it pool against the brick. Building codes require one on wider chimneys, and plenty of older homes do not have one.
Why Chimney Flashing Fails
- ✗Caulk and tar "repairs." Smearing sealant over the joint buys a season or two, then cracks. If you see black goop around your chimney, someone has been here before.
- ✗Counter flashing pulling out of the mortar. Freeze-thaw loosens the joint and the metal works free.
- ✗Old flashing reused during a reroof. A shortcut that saves time and leaves the oldest metal on the roof in the most important spot.
- ✗No cricket on a wide chimney. Water and ice pile up on the uphill side every storm.
- ✗Rust and corrosion on older steel flashing.
When It Is Not the Flashing at All
Sometimes the water is coming through the chimney itself, and no amount of new flashing will stop it.
- Cracked chimney crown. The concrete cap on top of the brick lets water straight down inside.
- Missing or damaged chimney cap. Rain falls right down the flue.
- Porous brick or failing mortar. Masonry absorbs water like a sponge in a driving rain.
A few clues, not a diagnosis: leaks that only show up in wind-driven rain from one direction often point to flashing on that side. Leaks that show up after almost any rain, or that appear inside the firebox, often point to the crown, cap, or masonry. The only way to know is to get eyes on it from the roof and the attic.
When we look at a chimney leak and it turns out to be a masonry problem, we will tell you that plainly so you can call a mason, instead of selling you flashing work that will not fix it.
How It Should Be Fixed
A real flashing repair means removing the shingles around the chimney, installing new step flashing woven into the courses, cutting new counter flashing into the mortar joints, and adding or rebuilding the cricket where one is needed. It is more work than a caulk job, and it is the version that lasts.
If your roof is due for replacement anyway, the chimney should get all new flashing as part of the job. Never let a contractor reuse the old metal. More on what a proper job includes in what to expect during a roof replacement.
Frequently Asked Questions
The most common cause is failed flashing where the chimney meets the roof. Other causes include a cracked chimney crown, a missing chimney cap, or porous brick and mortar. Leaks only in wind-driven rain often point to flashing, while leaks after almost any rain often point to the chimney itself.
Caulk or tar over failed flashing is a temporary patch. A lasting repair replaces the step flashing and counter flashing and adds a cricket where needed. If the roof is being replaced, the chimney should always get new flashing.
A cricket is a small peaked structure built on the uphill side of a chimney that diverts water and snow around it instead of letting it pool against the brick. Building codes require one on wider chimneys, and many older homes are missing one.
Start with a roofer to check the flashing, since it is the most common cause. If the problem is the crown, cap, or masonry, a good roofer will tell you and point you to a mason rather than selling flashing work that will not solve it.
Water Near the Chimney?
Faria & Son is owner-operated, and we will tell you exactly where the water is getting in before we quote a fix. Call 508-989-8383 or request a free estimate for roof repairs.
We serve Somerset, Swansea, Rehoboth, Westport, Seekonk, Fall River, and Freetown in Massachusetts, plus Warren, Barrington, and Tiverton in Rhode Island.