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Chimney · Catch it early

Spalling brick on the exterior stack

Face brick flaking means water has been getting in and freezing. Tuckpointing addresses it if caught before the units start failing structurally. You can handle this one yourself. No call needed.

Quick answerSpalling is when the face of a brick flakes, pops or crumbles off. On a chimney it means water has been getting into the masonry and freezing. Tuckpointing, which replaces worn mortar joints, addresses it if it’s caught before the bricks themselves start failing structurally. Just as important is stopping the water: a cap on the flue, a sound crown, and no sealants that trap moisture in the brick.

Chimneys take more weather than any other masonry on the house. They stand above the roof, get rain from every side, and freeze and thaw all winter. That’s why they’re often the first place brick shows its age.

A brick wall with broken, damaged bricks
Brickwork with broken, damaged faces. On a chimney, stop the water first, then deal with the brick and mortar. Photo by H&CO on Unsplash.

1Why chimney brick spalls

  • Water from the top. An open flue or cracked crown lets water into the masonry from above.
  • Worn mortar. Eroded joints let rain soak in between the bricks.
  • Freeze-thaw. Water in the brick freezes, expands, and pushes the face off.
  • Trapped moisture. Non-breathable coatings, or mortar harder than the brick, can hold water in and make spalling worse.

2How to check it

  1. Look from the groundUse binoculars. Look for flaking faces, crumbling joints, and bits of brick on the roof or in the gutters.
  2. Check the topSee whether there’s a cap on the flue and whether the crown looks cracked.
  3. Look for a leanA chimney that leans, or has loose or missing bricks, has gone past surface damage.
  4. Look insideWater stains in the attic around the chimney or in the firebox mean water is getting through.

3What to do about it

Do it yourself

Stop the water first. Fit a cap if the flue is open, keep gutters near the chimney clear, and watch the damage from the ground each season. If the stack is low and you’re experienced with masonry and safe roof work, small areas of worn mortar can be raked out and repointed with a mortar that’s softer than the brick.

Manageable yourself

  • Fitting a cap and fixing water sources
  • Monitoring from the ground
  • Small repointing jobs on a low, safe stack

Beyond a DIY job

  • A tall stack or a steep roof
  • Bricks loose, missing or cracked through
  • The chimney leans or the top is falling apart
Roof safety and falling brick

Don’t work on a roof alone, in wet weather, or without proper fall protection. If bricks are loose or the chimney leans, keep people away from below it and have it looked at, because falling masonry is dangerous.

Skip the clear sealer on damaged brick

Coatings that aren’t breathable can trap moisture in brick and make spalling worse. If you want a water repellent, use one made for masonry, and only on sound brick.

4What drives the cost

Caught early, this is a cap plus some mortar work. Costs rise with the height of the stack, the area of damaged brick, and whether the top of the chimney has to be rebuilt. It’s one of the jobs we list as something you shouldn’t be paying much for, as long as you deal with it early.

Chimney cost

5Questions

Can spalled bricks be repaired?

Lightly flaked bricks can often stay once the water is stopped. Badly spalled ones get replaced.

What is tuckpointing?

Raking out worn mortar joints and refilling them with fresh mortar. It keeps water out of the joints.

Should the new mortar be strong?

Not stronger than the brick. Mortar that’s harder than the brick can push damage into the brick instead of the joint.

Written by Jaylan Jones. I Like To Exterior Services earns a referral fee when a call connects to a contractor. See our business-model disclosure.