The answer first
Spalling is when the face of a brick flakes, pops off or crumbles away. It is almost always caused by water getting into the brick and then freezing, or by salts crystallising as the brick dries. The fix has two parts: stop the source of the water, then cut out the damaged bricks and replace them with matching ones set in a suitable mortar. Replacing bricks without dealing with the water usually means the new ones fail too.
Common causes
Hard cement mortar used to repoint soft old bricks is one of the most common causes, because it forces moisture out through the brick instead of the joint. Other causes are leaking gutters and downpipes, ground levels built up above the damp-proof course, missing copings on garden walls, sealants or paints that trap moisture, and bricks that were never meant for exposed positions. Bricks below damp-proof course and on chimneys and free-standing walls are the most exposed.
Fretting and salt damage
Fretting is a slower, sandy crumbling of the brick surface. It often comes with white salt deposits called efflorescence. Salts carried in by water are left behind as it evaporates, and their crystals break the surface. Brushing off the salts is fine, but the lasting fix is reducing the water.
How damaged bricks are replaced
The mortar around the damaged brick is cut out and the brick carefully broken out without disturbing its neighbours. A replacement brick of the right size, colour and texture is buttered with mortar and slid into place, then the joints are pointed to match. Where many bricks in one area are damaged, a section may be taken down and rebuilt. Reclaimed bricks are often the best match on older houses.
Can bricks be turned round?
Sometimes a solid brick can be removed and reversed so its undamaged back face shows. It only works on solid bricks with a good back face and where both faces look similar, but it can give a perfect colour match.
Avoiding it in future
Keep gutters and downpipes clear and sound, keep ground and paving below the damp-proof course, make sure garden walls have a coping with a drip, and use a mortar that is weaker than the brick when repointing. Avoid sealing brickwork with coatings that stop it breathing.
When to get it looked at
A few flaking bricks are a maintenance job. Widespread spalling, bulging, cracks or damp inside should be looked at properly, because they can point to a bigger problem with the wall or the drainage around it. Our guides on cracks in brickwork cover movement-related problems.
Choosing replacement bricks
Bricks vary in size, colour, texture and how much water they absorb. Imperial bricks on older houses are slightly larger than modern metric ones, so a straight swap may leave uneven joints. A good replacement matches size first, then colour and surface, and should be at least as durable as the originals for the position it is going into. Test a few candidates against the wall in daylight, wet and dry, before ordering.
About us
D & A Brickwork & Building is a family-run firm based in Bidwell, Dunstable. We have more than 26 years of building experience, our bricklaying is NVQ Level 2 qualified, we are members of the Federation of Master Builders and we are fully insured. Estimates are free and follow a visit to see the job.
Brick matching, repairs and repointing are part of our bricklaying work.
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Questions people ask
What causes bricks to spall?
Mostly water in the brick freezing, or salts crystallising as it dries. Hard mortar, leaks and high ground levels make it worse.
Can spalled bricks be repaired without replacing them?
Minor surface damage can sometimes be left or turned round, but badly spalled bricks are best cut out and replaced.
Will new bricks match?
A good match is usually possible with careful choice of new or reclaimed bricks and matching mortar and joint finish.
Should I seal my bricks to stop spalling?
Generally no. Many sealants trap moisture and can make spalling worse. Fix the source of the water instead.