Why are my chimney bricks flaking and the faces popping off?
Brick faces flake and pop off because water has soaked into the brick and is pushing the surface away from inside. This is called spalling, and it means the chimney is losing its protection against moisture.
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A few scattered flakes on an old chimney can be repaired by replacing individual bricks. Widespread flaking, or bricks shedding from the part above the roofline, usually points to rebuilding that section. A chimney technician can tell which it is once they have seen the brick up close.
Why it happens
Brick is porous. It takes on water in rain and releases it as it dries. When something stops that cycle working, the water stays in the brick. Where it freezes, it expands and breaks the face off. Where it carries salts or acids, it breaks the face down chemically. Either way the surface comes away in flakes or flat chips.
The usual causes are above the brick. A cracked or missing crown lets water run straight into the stack. Failed flashing and open mortar joints let it in at the sides. No cap leaves the top open to rain. Inside the chimney, a damaged or missing liner lets flue gases and condensation soak into the brick from the other side.
Surface treatments can make it worse. Paint or a sealer that is not made for masonry can trap moisture behind it. Repair mortar that is much harder than the original brick can also push the damage into the brick faces. That is one reason a patch often fails within a season or two.
What you can check yourself
Look from the ground
Use binoculars from the yard. Note whether the damage is only near the top or runs down the whole stack, and whether the chimney looks straight.
Look for debris
Check the ground, the lower roof edges you can see from a window, and the firebox for brick chips or grit. Fresh chips mean the damage is ongoing.
Look for white staining
A white powdery deposit on the brick means water is moving through the masonry. It helps a technician trace where the moisture is coming from.
Check inside the house
Look at the walls and ceiling around the chimney for stains or peeling paint, and notice any damp or smoky smell near the fireplace.
Check your alarms
Make sure the carbon monoxide and smoke alarms near the fireplace are working. Do not go on the roof or put anything into the flue.
When to call a technician
Do not use the fireplace if the stack is leaning, if bricks are coming loose, or if you find brick pieces in the firebox. If anyone has a headache or dizziness while a fire is lit, get outside and call 911.
Flaking brick does not heal, and the damage spreads as more water gets in, so it is worth having it looked at soon. Call One Call Chimney on (866) 576-7943 and we will arrange an independent chimney technician or mason. The estimate is free. The technician inspects the chimney and gives you the price before any work starts, and you approve it first.
Permit rules for masonry work differ by state, city and county. Ask your local building department whether a rebuild needs one. The technician can tell you what the work involves.
What the technician will do
- Inspect and photographThey look at the brick, mortar, crown, flashing and liner, and photograph what is failing. Ask to see the photos or camera footage and to have the reasoning in writing.
- Rebuild above the rooflineThis is the usual answer when the brick is breaking down. The damaged section comes down and is rebuilt with sound masonry.
- Full rebuild where the structure has goneIf the stack is leaning or the base has failed, the rebuild includes a proper footing and new flashing.
- New crown cap and linerThe crown and liner are part of the work, so the new masonry is protected from water and flue gases.
- Match brick and mortarBrick and mortar are matched as closely as the house allows, so the repair blends in and the materials work together.
Related questions
- Can I seal or paint the bricks to stop the flaking?
- Usually not. A coating over wet brick can trap moisture and speed up the damage. The water source, such as the crown, flashing or joints, has to be fixed first.
- Is a flaking chimney dangerous?
- It can be. Brick that is shedding may fall, and a weakened stack can lean. A fireplace should not be used under a stack that is leaning or shedding brick.
- Can just the damaged bricks be replaced?
- Sometimes, when the damage is limited and the rest of the masonry is sound. If the flaking is widespread or the mortar has failed throughout, replacing single bricks tends to be a short-term fix.
- What decides the cost of a repair or rebuild?
- Access and chimney height matter, as does how much brick has failed. The crown, flashing and liner condition also count, as do the materials needed to match the house. The free estimate sets the price after the technician has inspected, and nothing starts until you approve it.
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