If you have found thin, curved pieces of brick on the driveway or in the gutter beneath your chimney, you have seen spalling. AM Chimney Sweep repairs chimney brickwork in Teaneck and provides cleaning and inspection, and spalled brick is one of the clearest signals a chimney gives that water has been getting in for some time.
What spalling is
Brick is porous. It absorbs water in rain and releases it as it dries. When a brick is saturated and the temperature falls below freezing, the water inside expands and pushes the outer face away from the body of the brick. One night does little. Dozens of freeze and thaw cycles each winter, year after year, shear the face off. What is left is a soft, rough core that absorbs even more water, so the damage accelerates.
Why we see it in Teaneck
Census Bureau estimates show that about three-quarters of Teaneck’s homes were built before 1960, a third of them before 1940. Chimney brick of that age has been through a great many winters, and a chimney is the most exposed masonry on a house: it stands above the roofline with weather on all four sides and nothing sheltering it.
Source: U.S. Census Bureau, American Community Survey 2020–2024 five-year estimates.
Where the water is coming from
Spalling is a symptom. Replacing the damaged bricks without finding the water source only resets the clock. The usual sources:
- A cracked crown. Water enters at the top and saturates the courses just below. Spalling concentrated near the top of the chimney points here.
- No cap. Rain runs down the inside and soaks through the flue into the brick.
- Open mortar joints. Water sits in recessed joints and soaks into the brick edges.
- Hard patch mortar. Old, soft brick repointed with modern high-strength mortar cannot release moisture through the joints, so it leaves through the brick face and takes the face with it.
- Paint or a film-type sealer. A coating that does not breathe traps moisture behind it.
- Condensation inside the flue. A gas appliance venting into a cold, oversized flue can soak a chimney from the inside.
Reading the pattern
- Damage at the top few courses: look at the crown
- Damage on one face only: the weather side, or the side a flue runs closest to
- Damage beside earlier repairs: incompatible mortar
- Damage all over a painted chimney: trapped moisture
The right order of repair
- Stop the water. Repair or rebuild the crown, fit a cap, and correct any flue problem that is wetting the chimney from within.
- Replace the failed brick. Spalled bricks are cut out and replaced with brick matched as closely as possible for size, color and texture.
- Repoint. Worn joints are raked out and refilled with a mortar suited to the age of the brick.
- Rebuild where necessary. If most of the bricks above the roof are damaged or loose, it is sounder and often more economical to rebuild that section than to patch it.
Full details are on our masonry repair and repointing page.
Things to avoid
- Skim-coating spalled brick with cement. It hides the damage, traps water and falls off.
- Painting the chimney to “seal” it.
- Caulking cracks in brick or joints.
- Pressure-washing old brick, which drives water in and strips the surface.
How urgent is it?
A few spalled faces are not an emergency, but they will not stabilize on their own. Loose bricks at the top of a chimney are a different matter, because they can fall. If you can see bricks out of line or missing from the ground, have it looked at soon.
Schedule a masonry inspection in Teaneck
Call (862) 225-6529 or send us a request. We photograph the chimney from the roof, run a camera down the flue as part of the inspection, and explain what is causing the damage before proposing any repair. For a finished example, see our crown and masonry repairs in Rumson, or look through Our Work.