Chimney brick replacement and spalling repair in Fish Hawk

What spalling looks like on a chimney

Spalling shows as a brick face that has flaked, popped off in a layer or crumbled away, leaving a rough, recessed surface. Fragments may collect on the roof, in the gutter or on the ground below.

Broken or badly spalled brick lets moisture in, the Brick Industry Association notes, and the damaged units may have to be replaced. A spalled brick is not just a cosmetic blemish, because it lets more water into the masonry around it.

Our inspection records which units have lost their face and how deep the loss goes, so the repair area is based on the actual damage.

Mortar that is harder than the brick

Mortar is meant to be the weaker, more permeable part of a brick wall. The National Park Service explains that repointing mortar should be softer and more vapor permeable than the bricks, and that mortar stronger than the units can cause damage such as cracking and spalling.

When hard mortar surrounds softer brick, moisture and movement stresses end up in the brick instead of the joint. Replacing bricks in that situation without addressing the mortar can repeat the damage.

We compare the existing mortar and the bricks before choosing the repair mortar, and explain the choice on the estimate.

Water entering at the top of the chimney

The top of a masonry chimney is its first line of defense. Florida's residential code calls for that top to be a cap of concrete, metal or stone, finished with a drip edge and with a caulked bond break wherever a flue liner passes through.

When that cap or crown cracks, lacks a drip edge or has lost its seal at the flue, water can run down into the upper courses of brick. Those bricks may then spall or loosen first.

Where the brick damage is concentrated near the top, we inspect the crown closely and explain any crown repair on its own line of the estimate.

Testing the existing mortar

Matching the original mortar is easier when you know what it is. The Brick Industry Association notes that a laboratory can analyze a sample of the original mortar to estimate what it contains, in what proportions and how strong it is, generally following the methods of ASTM C1324.

Most chimney brick repairs do not need a laboratory report, but on older or unusual masonry it can be worth the time. We explain when testing would add value and when a careful comparison on site is enough.