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How Brick Crumbles

Learn what causes brick to crumble.

How Brick Crumbles

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Brick-veneer siding is applied to a wood frame over building paper. It can cover an entire wall, or serve as an accent to other exterior surfaces. You can tell the difference between a brick veneer and structural brick by the brick pattern. Structural brick normally requires two layers of bricks tied together every few rows. The ties are bricks placed on edge so you can see a row of the short ends of the brick.

Brick is amazingly durable and an excellent insulator, which is why it's so widely used and has been for centuries.

Older brick homes usually feature solid brick construction. Most modern brick homes, however, are made with brick veneers. These surfaces give the appearance of solid brick at a lower cost.

Both solid brick and brick veneer is applied with mortar, which is cement, sand, and lime mixed together with water. Both substances are solid yet porous, with mortar being more so. In wet climates, and especially climates that experience extreme temperature swings, water-repellant coatings are sometimes applied to brick buildings to preserve their finish.

Both types of brickwork can deteriorate for a number of reasons. Sometimes it's just one thing that causes the problem; other times it's a number of things that come together to create havoc.

Tool Chest

Spalling describes brick that is shedding its topmost layer.

Spalling happens when moisture inside the brick expands and contracts due to temperature changes. It causes brick to lose its topmost layer. It is more of a problem in climates with temperature extremes, and especially in areas where there are repeated freeze-thaw cycles.

Spalling can also indicate mortar that is too dense or too high in cement content. Mortar should never be denser than the brick it holds in place, but it definitely can be. When it is, it's stiffer than the brick that it surrounds, and it won't allow the bricks to expand as much as they need to when they get wet. Because of this, stress builds up inside the brick because the mortar doesn't let the moisture escape to the surface of the brick where it can evaporate. Instead, the surface cracks off due to the pressure.

Properly installed and maintained brick is less likely to develop spalling. That said, about the only way to fix spalling when it happens is to replace the affected bricks with salvage or replica pieces. Depending on the extent of the damage, it might be possible to remove individual bricks, clean them, and put them back into place with the undamaged side facing out.

For more extensive damage, painting the brick or applying a breathable, water-repellent coating might slow down additional deterioration.


Cracks in brickwork are pretty common and can happen either along mortar joints or in the bricks themselves. Typically, they're caused by things like structural movement, construction defects, temperature and moisture extremes, mortar problems and/or erosion, and tree roots growing too close to foundations. If you see cracks in mortar, these factors are most likely to blame.

Cracks in bricks, however, can indicate more serious problems, such as unstable soil, uneven weight distribution, and foundation problems.

Brick veneer sidings typically will develop cracks along mortar joints. Very rarely do the bricks in these surfaces crack.

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