Why are my chimney bricks flaking and crumbling on the face?
Flaking, crumbling brick faces are almost always caused by water. Moisture soaks into the brick, and when it freezes, dries out or carries salts to the surface, the outer face pops off in flakes. The trade calls this spalling.
Phones answered around the clock · free estimate
The flaking is a symptom, not the whole problem. Water is getting in somewhere, usually through the crown, the flashing, worn mortar joints or a missing cap. If only the bricks are replaced, the new ones will start to fail too.
Why it happens
Brick is porous. It is built to take on a little water and release it again. A chimney stands fully exposed above the roofline, so it takes the worst of the rain and wind. When something above or around the brick stops shedding water, the brick stays wet for long periods and the face begins to break away.
The usual entry points are a cracked or crumbling crown (the cement slab across the top), flashing that has lifted or rusted where the chimney meets the roof, mortar joints that have eroded, and a flue with no cap. Brick that has been repointed with mortar that is too hard for it, or coated with something that traps moisture inside, can also spall.
A chimney that has been wet for years can become structurally unsound. Loose brick can also fall, which is a hazard at the base of the chimney. That is why the cause should be traced and fixed rather than patched over.
What you can check yourself
Look from the ground
Stand well back and look up the stack, using binoculars if you have them. Note whether the damage is near the top, near the roofline or all the way down.
Look for debris below
Flakes or chunks of brick on the ground, a lower roof or a ledge show how active the damage is. Keep people and pets away from the base while you are unsure.
Check for damp indoors
Look at the ceiling and walls next to the chimney, and inside the firebox, for stains, peeling paint or a damp smell. These suggest water is travelling further than the brick face.
Look for white powder
A pale, chalky deposit on the brick is salt carried out by moisture. It confirms the masonry is staying wet.
Leave the roof alone
Do not climb up or put anything into the flue to inspect it. A technician can do this safely and with a camera.
When to call a technician
Call once you see flaking brick, even if it looks cosmetic. The damage gets worse the longer water keeps getting in. Call sooner if bricks are loose or falling, mortar is missing in patches, the stack leans, or you have damp marks on the ceiling beside the chimney. If you see fragments inside the firebox or smoke comes into the room, stop using the fireplace until it has been inspected. If anyone has a headache or dizziness, get outside and call 911.
One Call Chimney is a referral and scheduling service. One call to (866) 576-7943 arranges an independent sweep or mason to inspect the chimney. The estimate is free, the technician gives you the price before any work starts, and you approve it first. Permit rules for masonry repair or rebuilding vary by city and county, so check with your local building department.
What the technician will do
- Trace the entry pointThe technician looks for where the water gets in, rather than sealing over the damage. Ask to see photos or camera footage of what they find.
- Repair the crown and flashingA cracked crown is repaired or recast. Flashing is replaced and counter-flashed into the mortar joint, and a cap is fitted if there is none.
- Repoint and replace brickEroded mortar is repointed and badly spalled brick is cut out and replaced. Ask for the reasoning in writing.
- Protect the masonryWhere appropriate, a breathable water repellent is applied once the repairs are done, so the brick can still release moisture.
Related questions
- Can I just paint or seal the crumbling bricks?
- Painting or sealing over damaged brick does not stop the water getting in. A coating that traps moisture can make spalling worse. A breathable water repellent can help, but only after the leak is fixed and the damaged brick and mortar are repaired.
- Can individual bricks be replaced?
- Yes. Spalled bricks can usually be cut out and replaced, and the surrounding mortar repointed. If the damage is widespread or the structure has moved, a mason may recommend rebuilding part of the stack.
- Is it safe to keep using the fireplace?
- It depends on how far the damage goes. Surface flaking on the outside is not the same as a damaged flue, and only an inspection can tell the two apart. If pieces are falling inside, or smoke enters the room, stop using the fireplace until it has been checked.
- What affects the cost of repair?
- The main factors are how high and how easy the chimney is to reach, how much brick and mortar is damaged, and whether the crown, flashing or cap also need work. The free estimate covers these, and you agree the price before anything starts.
Get a technician out
Free estimate. The price is agreed before the work starts.
Or send us a message
Leave your details and what is going on, and someone from the team will call you back.
More from One Call Chimney
Keep reading
One Call Chimney arranges the visit; the technician does the work and gives you the price.