Environmental Chimney Sweep Inc.

What is Spalling?


Spalling: An Explainer

When Basic Chimney technicians talk with our clients about their chimney systems, we wish we could always stick with the fun stuff: cozy fires, crackling logs, beautiful masonry design. But chimneys are hardworking systems that are under almost constant assault inside and out, from the heat of your fire to the pounding rain and beating sun outside. So, unfortunately, we need to talk about the less-fun stuff sometimes too, to help keep you informed about your system’s needs.

One of the more frustrating words that can come up when talking about a chimney system: spalling. Essentially, spalling refers to crumbling, cracking and/or flaking masonry — and that can take a variety of looks and forms.

What Does Spalling Look Like, And How Does It Happen?

Water is your chimney's number one foe. Spalling is one negative result of excess moisture.

Water is your chimney’s number one foe. Spalling is one negative result of excess moisture.

Depending on what led to your problem and the particular material (brick, mortar or concrete), your spalling masonry can have a few different looks — anything from surface chipping to bricks that look like they’ve more or less exploded from the inside out. You might see bricks that seem like their faces have completely popped off, leaving uneven, broken and receded areas on a once-straight chimney stack. You might see a chimney crown that’s crumbled and flaked, anything from a rough and ragged surface to looking almost like someone took a sledgehammer to it.

In particularly bad cases of spalling, your masonry has more or less burst from the inside out: Moisture gets absorbed into the chimney, and then as winter chills roll in, that moisture freezes and expands, putting serious, unrelenting pressure on your not-very-pliable bricks and mortar. Then, boom: spalling masonry.

But it’s not always the freeze/thaw cycle. Sometimes spalling is the result of age, and long-term wear-and-tear from weather on your masonry surface. Spalling can also be the result of do-it-yourselfer errors, like putting latex paint on your chimney (which ends up trapping moisture inside your chimney and doing far, far more damage than good). Whatever the cause, it’s a serious problem and an almost surefire contributor to chimney leaks (and the damage and potential mold that can come along with those leaks), so proper repairs need to be made as soon as possible.

What Can I Do About Spalling Masonry?

There’s no two ways about it: Spalling masonry needs to be repaired properly by experienced, knowledgeable chimney technicians like the ones at Basic Chimney Sweep & Repair. We can assess the level of damage and recommend the right repairs — anything from rebuilding your chimney crown to restoring your chimney stack. And once those repairs are made, we can also recommend some ways to help you avoid similar problems in the future, like adding a specially formulated waterproofing sealant to your chimney to help your masonry repel moisture and protect it for years to come.

The best thing you can do, though, is to try and avoid spalling to begin with. And keeping up with your annual chimney inspections is a good start toward that goal. If Basic Chimney technicians are able to examine your system closely every year, we’ll find small problems (and make the necessary repairs) before those problems become a big headache, like a spalling, crumbling chimney crown.

Do you have any questions or concerns about spalling or other kinds of masonry damage? We’re always glad to help our valued clients. Just give Basic Chimney Sweep & Repair a call!



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National Chimney Sweeps Guild Chimney Safety Institute of America