Chimney Leaking When It Rains? 5 Causes and How to Fix Each One

A brown stain on the ceiling beside the fireplace. A drip in the firebox after a storm. Wallpaper that bubbles above the mantel. If you see water around your chimney when it rains, you have a chimney leak.

The five common causes are flashing, the chimney crown, the chimney cap, the brick and mortar, and, on prefab chimneys, the chase cover. Each one leaves different clues.

Why Chimney Leaks Are Hard to Find

Water travels. It can get in at the top of the chimney, run down inside the masonry and show up on a ceiling several feet away. That is why a roofer may seal the flashing and the leak keeps coming back. The water was never coming in at the flashing.

Finding the entry point comes first. Here is what to look for.

1. Flashing: Where the Chimney Meets the Roof

Flashing is the sheet metal that seals the joint between the chimney and the roof. It is the most common source of a leaking chimney.

Good flashing has two layers. Step flashing is woven in with the shingles. Counter flashing is cut into the mortar joints and folds down over it. Over time the sealant dries and cracks in the Texas sun, wind lifts the metal, and the house settles and pulls the roof away from the chimney.

Clues: stains on the ceiling or wall right next to the chimney, wet roof deck in the attic around the chimney, and leaks that are worse in wind-driven rain.

2. A Cracked Chimney Crown

The chimney crown is the concrete or mortar slab on top of your chimney, around the flue. Its job is to shed water away from the brick. When it cracks, rain runs through the cracks into the masonry below.

Clues: water stains high on the chimney, white chalky deposits on the upper bricks, and bits of mortar on the roof. See chimney crown repair.

3. A Missing or Damaged Chimney Cap

With no cap, rain falls straight down the flue. In a heavy rain, that is a lot of water.

Clues: water or rust in the firebox, a rusted damper, and a drip you can hear inside the fireplace during a storm. A new chimney cap is one of the simplest repairs there is.

4. Brick and Mortar That Soak Up Water

Brick is porous, and old mortar joints crack and wear away. In a long rain the whole chimney stack can soak through like a sponge.

Clues: damp patches on the inside wall behind the chimney, white stains on the brick, flaking brick faces and sandy mortar joints. The fix is new mortar, called tuckpointing, followed by a breathable water repellent. See chimney waterproofing.

5. A Rusted Chase Cover

Many Dallas homes built since the 1980s have a prefab chimney: a metal flue inside a framed box covered with siding. The top of that box is sealed with a flat metal chase cover. The original covers are often thin galvanized steel. They sag, hold water and rust through.

Clues: rust streaks running down the siding, and water in the firebox or stains on the ceiling near the fireplace.

What to Do Right Now

1. Catch the water. Put a bucket and towels under the drip.
2. Take photos of the stain and the water. They help with the repair and with insurance.
3. Do not light a fire in a fireplace that has water in it.
4. Look in the attic with a flashlight, if it is safe, to see where the roof deck is wet.
5. Call for an inspection. The sooner the leak is found, the less wood has to be replaced.

Why Dallas Chimneys Leak

North Texas weather is hard on a chimney. Spring brings hail that cracks crowns and dents caps. Storms bring heavy rain in short bursts, often with strong wind. Summer sun dries out sealant. And the clay soil under our homes moves, which opens gaps between the chimney and the roof. You can follow local storms at the National Weather Service office for Dallas-Fort Worth.

How We Find and Fix a Chimney Leak

We check the roof, the attic and the firebox, and we take photos so you can see exactly where the water gets in. Then you get a written price. Our chimney leak repair in Dallas is 10% off, and the estimate is free.

A yearly chimney inspection catches most of these problems while they are still small.