If you've found a pile of thin brick chips at the base of a wall, or a brick with its whole outer face missing like someone peeled an orange, that's spalling. Not cracked mortar, not dirt. The brick itself has lost its fired outer skin, and once that's gone it doesn't grow back. What's underneath is softer, more porous, and on its way to the same fate unless something changes.
What's actually failing
A brick is fired hardest on the outside. That thin outer face is what sheds water and takes the weather. Spalling is that face breaking off, usually in flat chips or curved flakes, and exposing the weaker, more absorbent brick underneath. Once the face is gone, the exposed core soaks up water faster than the brick around it did, so the damage accelerates instead of stopping.
Two things drive most of it in this area.
Freeze-thaw with nowhere for the water to go. Water gets into the brick through a hairline crack, a porous face, or a mortar joint, then freezes and expands. London runs through dozens of freeze-thaw cycles every winter, and each one is another chance for trapped water to push a little harder. Eventually the face pops.
Repointing with the wrong mortar. This is the one we see weekly on London's older stock, and it's almost always avoidable. Original mortar on pre-1950s brick was a soft lime mix, weaker than the brick itself, on purpose. The joint was designed to be the sacrificial part, the piece that cracks and gets redone every few decades so the brick doesn't have to. Repoint that same wall with a modern hard Portland cement mortar, and you've flipped the hierarchy. Now the mortar is harder than the brick, water can't move through the joint the way it used to, and the brick face takes the beating the mortar was supposed to absorb. We've pulled apart Old North and Woodfield walls where a five-year-old repointing job, done with the wrong mix, had already put more stress on the brick than fifty years of the original mortar ever did.
Salt plays a role too, especially on brick near a driveway, walkway, or a wall that gets splashback from de-iced pavement. Dissolved salt works its way into the brick, then crystallizes as the wall dries, and those crystals push outward from the inside exactly the way ice does.
Check your brick this weekend
You don't need a ladder for the first pass. Walk the exterior and look specifically at three zones: the courses closest to grade, anything under a downspout or gutter joint, and north-facing walls that stay damp longest after rain. Those are the spots that cycle through wet and freezing the most, so they spall first.
Look for the face itself missing or curling away, not just a crack in the mortar. Then check the mortar joints near any damage. If the mortar looks bright grey, perfectly smooth, and noticeably harder or newer-looking than the brick around it, that's worth flagging even if nothing has spalled yet. It tells you someone repointed with the wrong mix, and the brick around that repair is now carrying a load it wasn't built for. You can find more on telling a normal repair from one that's working against the wall in our piece on common masonry problems we see on London homes.
Where DIY stops making sense
A homeowner can absolutely do the walk-around inspection above, and it costs nothing. What you shouldn't do is try to fix a spalled brick face yourself with a patching compound, brick-colored caulk, or a masonry sealer. Skimming a compound over the damaged face or sealing the wall traps whatever moisture is already inside the brick, and the next freeze has less room to expand into, which usually makes the spalling worse and spreads it to brick nearby that was fine before you touched it.
The actual fix for spalled brick is replacing the damaged units, cutting out the failed brick and setting in a matching replacement, then repointing around it with a mortar mix that's appropriately softer than the brick, not harder. That takes sourcing brick that matches your wall's age, color, and size, which on London's yellow brick heritage stock is its own skill, plus mixing mortar to the right hardness for what's actually there. That combination is a mason's job. If the spalling is limited to a handful of bricks, it's a small, contained repair. If it's spreading across a wall, or you're seeing it on brick that was repointed in the last decade, get it looked at before it takes out more of the wall. A brick repair assessment is free, and every job gets priced after we've actually seen the wall, since the fix depends entirely on how far it's spread and what brick is available to match.
Frequently asked questions
Can spalled brick be repaired without replacing it?
Not really, once the face is gone. The fired outer skin doesn't come back, and covering it with a patch or sealant traps moisture and tends to make it worse. Replacing the damaged brick units is the fix that actually holds.
Is spalling a sign my whole wall is failing?
Not usually. Spalling is a brick-by-brick problem driven by water getting into individual units, not a structural issue with the wall as a whole. It's worth a proper look if it's spreading fast or showing up on brick that was recently repointed.
Does painting over spalled brick stop it from getting worse?
No, and it can speed up the damage. Paint and sealers block moisture from evaporating out of the brick the way it's supposed to, so water that gets in stays in longer and does more damage on the next freeze.
Why does spalling show up more on old London homes?
Older brick was fired to be paired with a soft lime mortar that was meant to wear out first. A lot of that brick has since been repointed with harder modern mortar, which shifts the freeze-thaw damage from the joint onto the brick itself.