Wilmington chimney losing its brick face: reading spalling on a river-town stack
The brick on this Wilmington chimney was shedding its face in coin-sized flakes. That is not weathering. That is water that got in and then froze.
What spalling actually is
Brick is not uniform all the way through. It has a hard fired face and a softer, more porous body behind it. When water soaks into the body and then freezes, it expands and pushes the face off from behind. You get flakes and shallow craters, often with a lighter, sandier colour showing underneath. That is spalling, and it only moves in one direction.
It is easy to confuse with ordinary surface wear. The test we use is simple: run a thumbnail over it. Weathered brick is worn but solid. Spalling brick gives up grit, and the edges of the crater feel soft. If a flake comes away in your hand, the water is already inside.
Why Wilmington stacks see more of it
Wilmington sits on the Kankakee River, and the older housing stock near the water carries a lot of soft nineteenth and early twentieth century brick that was never meant to be saturated. Humidity near the river keeps masonry damper for longer after rain, so there is more water held in the brick when the first hard freeze arrives in November.
The other local factor is the mortar. A lot of these chimneys were repointed at some stage with a modern portland-heavy mix, which is harder than the brick around it. When the wall cannot move or breathe through the joints, the water and the stress go through the brick face instead. We see neat repointing and badly spalled brick on the same stack surprisingly often.
What can be saved and what cannot
Individual spalled bricks can be cut out and replaced, and that is the right answer when the damage is scattered. Once a whole face has gone soft, or the stack has lost enough material that the courses no longer sit square, the honest answer is a rebuild from the damage line up. We will not sell a patch over masonry that needs taking down, because the patch fails in a season and you pay twice.
Either way the water has to be stopped first, which usually means the crown and the cap. We work to the NFPA 211 standard when we assess a stack, and we photograph what we find so you are looking at the same thing we are before you decide. Pricing for masonry work is published on our pricing page.
If this sounds like your house: we handle chimney repair across Kankakee County, and our Wilmington page covers what we usually find there. Call (815) 449-4264, 7am to 9pm, any day.
Quick questions
Can spalling brick be sealed to stop it?
Not once the face has gone. A breathable water repellent helps protect sound masonry, but sealing damaged brick traps moisture behind it and usually accelerates the failure.
Does spalling mean the whole chimney needs rebuilding?
Not necessarily. Scattered damage can be cut out and replaced brick by brick. A rebuild is for when the material loss is widespread or the courses have moved.
Why is it worse near the top?
The top of the stack gets the most rain, dries slowest and has the least mass around it. If the crown is cracked it is also taking water straight down into those courses.
Is spalling brick dangerous?
The masonry itself can become unstable if enough material is lost, and the same water that caused it is usually getting into the flue. It is worth an inspection rather than a guess.
Published October 26, 2026 · By Jacob Dove, Friendship Chimney Sweep, Bourbonnais IL