Spalling Bricks on Your Chimney: Causes and Fixes
Published October 9, 2026 · More articles
You look up at the chimney and notice the bricks don't look right. Some have rough, pitted faces. Some have chunks missing. There are brick chips on the roof or in the gutter. And you're wondering how long that chimney will stay standing.
The Problem
Spalling is when the face of a brick flakes, peels or pops off. It happens when water soaks into the brick, freezes, expands and breaks the surface apart. Do that enough times and the brick loses its hard outer layer, then starts crumbling from the inside out.
Chimneys get hit harder than any other part of a building. They stick up above the roof, so wind-driven rain hits every side. They have no overhang to protect them. And Chicago's long winters bring repeated freeze-thaw cycles, so the same water can freeze and thaw many times in a single season. That's why spalling bricks on chimneys are so common on bungalows in the Bungalow Belt, two-flats in Avondale and Bridgeport, and older homes in Beverly and Rogers Park.
The worry isn't just looks. Damaged chimney brick lets water into the chimney and the house, and loose pieces can fall onto the roof, a walkway or a neighbor's property.
What Causes Chimney Bricks to Spall
Water getting into the brick
Every case of spalling starts with water. The question is where it's coming from.
A cracked or missing chimney crown
The crown is the concrete or mortar cap on top of the chimney. When it cracks, rain runs straight into the top courses of brick. Spalling that starts at the top and works down often points here.
Worn mortar joints
Open, crumbling joints let water into the masonry. Once inside, it has nowhere to go but through the brick.
No chimney cap
Without a cap, rain falls straight into the flue and soaks the masonry from inside.
Sealers that trap moisture
Some coatings and paints keep water from escaping the brick. When that trapped water freezes, the face pops off. Freeze thaw brick damage often shows up a few winters after the wrong sealer goes on.
Hard mortar in old repairs
Mortar that's harder than the brick forces the brick to absorb the stress. On soft Chicago common brick, that leads to cracked and spalled edges right along the joints.
Signs to Look For
- A brick face flaking off, or pitted, rough-looking bricks
- Brick chips or sand on the roof, in the gutters or on the ground
- White staining (efflorescence) on the chimney
- Cracks in the crown or gaps around the flashing
- Water stains on the ceiling or walls near the chimney inside
- A chimney that leans, even slightly
What You Can Safely Check Right Now
- Look from the ground with binoculars or a phone zoom. Photograph each side of the chimney.
- Check gutters and the roof edge for brick chips after a storm.
- Look inside at the ceiling, walls and attic around the chimney for water stains.
- Note whether there's a cap on top of the flue.
- Don't climb onto the roof to inspect it yourself. Chimneys are high, roofs are steep, and loose brick is unpredictable.
- Don't paint or seal the brick to cover up the damage. That usually makes spalling worse.
When to Call Instead
Call if bricks are missing chunks, if pieces are landing on the roof or ground, if water is getting inside, or if the chimney is leaning. Each winter of freeze-thaw makes damaged brick worse, and spalling tends to speed up once it starts. A small spalling brick repair this fall can become a partial chimney rebuild in a year or two.
If the chimney is leaking into the house, our post on water coming down the chimney when it rains covers the leak side of the problem.
The Plan
- Call (773) 389-2576 or send the form. Tell us what you're seeing on the chimney and whether there are leaks inside.
- We inspect the chimney. We check the brick, mortar, crown, cap and flashing to find where the water is getting in, not just which bricks look bad.
- You get a clear price before work starts. The repair could mean replacing damaged bricks, repointing joints, rebuilding the crown, or, if the damage is extensive, rebuilding the top of the chimney. See chimney repair and brick repair for what each involves.
The win: a solid, watertight chimney that gets through winter without shedding pieces onto your roof.
Frequently Asked Questions
What causes spalling bricks on a chimney?
Can spalled bricks be repaired, or do they need to be replaced?
Is a spalling chimney dangerous?
Should I seal my chimney bricks to stop spalling?
Stop Water Before It Gets Behind the Brick
Crumbling mortar lets water in, and Chicago's freeze-thaw winters do the rest. Tell us what you're seeing. Call (773) 389-2576 or send the form.
- Inspection first, with photos of what needs work
- Written estimate before anything starts
- Serving Chicago & Chicagoland