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Spalling Or Crumbling Brick Faces
The front face of bricks is flaking, blowing off or crumbling away, leaving the softer inside exposed.
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What's happening?
A fired clay brick has a dense outer skin and a more porous core. Spalling is the loss of that skin. Water gets into the brick, then something expands inside it — ice, or salt crystals growing as the brick dries — and the pressure pops the face off in flakes. Once the skin has gone, the exposed core soaks up water far faster than the original face did, so the damage accelerates. That is why spalling spreads outwards from the first few bricks. The pattern tells you the cause: a band low down near the ground points at ground salts and splashing, damage concentrated below a cill or a leaking joint points at that leak, and damage across a whole wet elevation after a hard winter points at frost.
What usually causes it?
- Freeze-thaw damage where saturated bricks froze, which is why it shows worst on the wettest elevations
- Salt crystallisation inside the brick, from ground salts, de-icing salt, or salts left by an old chemical treatment
- Cement pointing or cement render trapping moisture in the brick so it can only escape through the face
- Bricks used in the wrong position for their frost rating, commonly a facing brick used below ground level or in a parapet
- Sandblasting or aggressive chemical cleaning that stripped the fired skin off in the first place
- A persistent water source — leaking gutter, failed cill, splashing path, blocked downpipe — soaking one area
- Soluble sulphates reacting in permanently damp brickwork, breaking the face down from within
Is it dangerous?
It is a durability problem far more than a collapse risk, but it does not stay cosmetic. Each spalled brick is now a sponge, so spalling drives penetrating damp and can wet the inside face of a solid wall. Deep loss across many bricks reduces the effective thickness of the wall, which matters on a single-skin garden wall, a parapet or a chimney stack where there is no second leaf. Loose flakes falling from height onto a path or a pavement are a hazard in their own right. What you should not do is seal it: a waterproofing coating over spalled brick traps the moisture behind it and usually makes the next winter worse.
Can I fix it myself?
Diagnosis yes, repair rarely. You can very usefully work out what is keeping those bricks wet — stand outside in heavy rain and watch where water actually goes, check the gutter joints and the downpipe, look at whether a path or a raised bed is splashing or bridging. Brushing off loose flakes is harmless. What does not work is filling spalled faces with mortar or a repair render, which sits proud, fails within a season and traps water; nor does painting the wall with a sealer. Cutting out and replacing bricks is skilled work because the surrounding wall has to stay supported.
When should you call a bricklayer?
Call a bricklayer when faces have blown off rather than just weathered, when the damage is spreading year on year, when it is on a chimney, parapet or above head height, or when damp has appeared inside behind it. Call sooner if flakes are falling onto a path or pavement, or if the spalling is on a garden wall where there is no second leaf to fall back on.
What will the bricklayer actually do?
- Identify why those bricks are saturated before replacing anything, since new bricks in a wet wall spall too
- Cut out spalled bricks and tooth in replacements matched for size, colour, texture and frost resistance
- Reverse the cause where it is the finish — remove cement pointing or render that is trapping moisture in the brick
- Rebuild rather than patch where a parapet, cill course or chimney has lost too much of its thickness
- Repoint the surrounding joints in a mortar weaker than the brick so the joint stays sacrificial
- Correct the rainwater or ground-level fault feeding the area, or refer it to the trade that owns it
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