Chimney Leak Repair

Signs of a chimney leak

Water from a chimney doesn't always show up next to the chimney. It can travel along framing, soak into the masonry and appear days after a storm. These are the signs that usually bring homeowners to us:

• Brown or yellow stains on a ceiling or wall that touches the chimney
• Peeling paint, bubbling wallpaper or soft drywall around the chimney breast
• Water, rust flakes or a musty smell in the fireplace or on the damper
• White, powdery deposits (efflorescence) on the brick, inside or out
• Brick faces that flake or pop off, or mortar joints you can scrape out with a fingernail
• Damp spots in the attic around the chimney after rain

Where the water usually comes from

Most chimney leaks trace back to one of a handful of places. Often there is more than one, which is why a single quick fix sometimes doesn't hold.

Our guide Why is my chimney leaking? explains each of these in detail, with a diagram.

How we find the source

1. We start with your observationsWhen the leak appears, how long after rain, whether wind direction matters, and where inside you see water. Photos of the stain help.
2. We look at the outsideCrown, cap, flue tile, brick, mortar joints and flashing, from the roof when it's safe to get up there.
3. We look insideThe firebox, damper, smoke chamber and flue, using a chimney camera where the flue allows.
4. We check the attic if we can reach itWet framing or sheathing around the chimney helps separate a flashing leak from a masonry leak.
5. We test when the cause isn't clearA controlled water test, wetting one area at a time, can confirm which part is letting water through.
6. You get written findingsPhotos of what we saw, the most likely source or sources, and the repair options.

Repair options

The right repair depends on what failed and how far the damage has gone. These are the repairs we use most often for leaks:

Chimney cap

A cap with a screened, covered top keeps rain out of an open flue. On multi-flue chimneys a full-width cap can cover all of them.

Crown repair or rebuild

Small cracks in a sound crown can be sealed with a crown coating. A crown that's thin, flat or breaking apart is better rebuilt to shed water past the brick.

Repointing and brick replacement

Grinding out failed mortar and repacking the joints, and replacing bricks that have spalled. Mortar is matched to the existing brick so it doesn't trap water.

Flashing repair or replacement

Resealing or replacing the step flashing and counterflashing so water is directed onto the roof instead of behind it.

Waterproofing

A vapor-permeable water repellent made for masonry, applied after repairs. It slows water absorption while letting the brick dry out.

Liner work for condensation

When the problem is condensation, the fix is usually a correctly sized liner for the appliance, not exterior sealing.

Repair, rebuild or replace?

We'll tell you which category your chimney falls into and why. As a general pattern:

• Repair fits when the damage is limited to one component and the masonry around it is sound.
• Partial rebuild fits when the top courses of brick are loose or badly spalled, which is common above the roofline where weather hits hardest.
• Larger rebuilds come up when a chimney leans, has extensive cracking, or water has damaged it well below the roof.

If the leak turns out to come from the roof itself rather than the chimney, we'll say so and explain what we saw, so you can bring in the right trade.

What a repair can and can't do

A good leak repair stops water at the point where it was getting in. It doesn't make old masonry new, and a chimney with several weak points can develop a second leak after the first is fixed. Saturated brick can also keep releasing moisture for a while after the repair. We'll be clear about which of these apply to your chimney, and we won't promise more than the repair can deliver.

Interior repairs, such as drywall, plaster and paint, are a separate step once the leak has stopped and the area has dried.

Questions homeowners ask