A chimney is a column of brick sitting on a sloped roof, and water reaches it from every direction. It runs down the roof into the uphill side, falls on the top, and soaks into the masonry. A leak that looks like a roof problem may be coming from any one of several parts.
The flashing at the base
This is the usual suspect. Chimney flashing has two layers: base flashing that sits on the roof, and counterflashing set into the mortar joints above it. When the sealant at those joints cracks or the metal rusts or pulls loose, water runs behind it. A wide chimney can also trap water behind it on the uphill side. Roofers sometimes add a cricket, a small peaked structure that diverts water around the chimney instead of letting it pool. Learn the signs of failed roof flashing to confirm it.
The crown
The crown is the slab of mortar or concrete across the top of the chimney, around the flue. When it cracks, water gets into the brick below and works its way down. You can often spot hairline cracks or crumbling edges from a distance.
The brick and mortar
Brick takes in water and freezes when it is cold. Over repeated freeze and thaw cycles, which are a normal part of winters in northern Illinois, that can crumble mortar joints and flake the face off bricks. Once the joints open up, water has an easy path in. White powder on the brick, called efflorescence, shows moisture is moving through the masonry.
The cap and flue
A chimney without a cap lets rain fall straight down the flue. That can show up as water in the firebox, rust on the damper, or a musty smell near the fireplace.
Signs inside
- a stain on the ceiling or wall near the chimney
- water or rust in the firebox
- peeling paint or wallpaper on the chimney wall
- a damp smell near the fireplace after rain
Who fixes what
Part of this is roofing and part of it is not. A roofer handles the flashing and any cricket. A mason handles the crown, the mortar, and the brick. A chimney sweep or chimney specialist handles the cap and the flue. We will tell you honestly which part is which after we look at it, so you are not paying a roofer to do a mason's job.
Be careful with waterproofing coatings on brick. The wrong product can trap moisture inside the masonry and make the damage worse. Ask the mason before you apply anything.
What to do now
If you see a stain near the chimney, put a bucket under any drip and photograph the stain. Check the flashing and crown from the ground with binoculars, but stay off the roof. Read our guide to finding a roof leak for more steps.
Get the chimney checked
Call Roof Leak Repair Carol Stream IL at (630) 866-1445 and tell us where the stain is. We can look at the flashing and tell you whether the problem is the roof or the chimney itself. Our roof leak repair team handles chimney flashing and more.
Carol Stream Leak & Restoration is a free referral service. We connect Carol Stream homeowners with independent local roofing contractors — no fees to you, ever. Call (630) 866-1445 for fast help with a roof leak.