Why Do Bricks Crumble (Spall) and is it Dangerous?

Why Do Bricks Crumble?

Bricks crumble when water inside the brick expands as it begins to freeze in cold weather. The expansion causes cracks and, over time, as this process repeats itself, the bricks will deteriorate until they crumble. The damage caused by the freeze-thaw cycle is known as spalling.

The first time water inside a brick freezes it will create a small internal crack that is insignificant. However, each time it is damp, water will gather in this crack and expand when temperatures drop. Each cycle will make the crack bigger until it blows the brick, causing the face to crumble and flake away.

Where there is spalling there is also likely to be efflorescence, which are salts that turn bricks white. When the water inside the brick that causes spalling escapes to the surface, it transports salt to the face of the brick, which leaves behind a white powder.

Are Spalling Bricks Dangerous?

Brick badly damaged by spalling and surrounded by efflorescence

Small amounts of spalling on external bricks is not dangerous and is only an aesthetic issue. However, if the crumbling is substantial and extends more than 20mm into the brick, then this has the potential to cause structural issues and does pose a risk.

Even if the depth of the damage is not 20mm deep, it will eventually need attention. If a brick has already started crumbling, there is nothing to suggest that it will stop all of a sudden. Therefore you will need to monitor the extent of the crumbling as it will naturally get worse.

Spalling also suggests that damp is present in the wall. If the brick is part of a wall exposed to wet weather then this is not a surprise, but if it is an internal brick, then this is cause for alarm. Internal damp can lead to rot, mould, and can eventually compromise the integrity of walls.

We suggest you contact a builder or damp inspector to take a look at the wall and provide recommendations if you are worried about flaking bricks. Checkatrade suggests you should be paying between £12-£26 for every brick that needs to be replaced.

Can Crumbling Bricks Be Repaired?

You cannot repair a crumbling brick, but it can be replaced. Masonry specialists will be able to remove the spalled brick and insert a new one. In some cases, if the brick is not too badly damaged, they may simply turn the brick around and hide the cracked side.

Bricks that are earlier in the spalling process and not completely deteriorated are easier and therefore cheaper to replace.

It is worth using an experienced tradesperson for this job as it is difficult. Not only does the brick need to be carefully cut out of the wall, but it needs to be a colour matched. If the brick is not a like-for-like replacement, it may stick out and look odd.

How Do You Stop Bricks From Crumbling?

The best way to stop bricks from crumbling is to apply a sealant that prevents water from penetrating the brick. If there is no water in the brick, then it will not expand in freezing temperatures. Use a breathable sealant that prevents water ingress while still allowing moisture to escape.

If you use a non-breathable brick sealant, it will keep the water out, but it will also trap existing moisture in the brick. This may actually worsen damp problems.

Check to see if there is anything that could be done to reduce the wall’s exposure to water before applying a sealant. For instance, it may be that spalling is only occurring around a drain pipe, which could mean that the pipe is leaking. Inspect gutters to ensure they are not full of debris, causing rain water to overflow and spill on to the wall.

Spalling is particularly common on facing bricks, which are porous and absorb a lot of water compared to engineering bricks.

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