The Ultimate UK Guide to Spalling Bricks and How to Fix Them
The Ugly Truth About Blown Bricks
I have spent well over 14 years on building sites across the UK and there is one sight that always makes a homeowner panic. You walk out one morning and notice little flakes of red clay sitting on the patio. You look up and see the face of your brickwork literally peeling away like an old sunburn. In the trade we call this spalling or blown bricks and it is a massive red flag. It means your walls are losing their first line of defence against the elements and taking on water.
Brickie Pro Tip
If you have only just spotted a few flakes on the floor do not panic. Most early spalling is purely cosmetic at the start. It is a warning sign rather than an immediate structural collapse so we have time to get it sorted before things get properly expensive.
In this guide I am going to walk you through exactly what is happening inside your walls. We will look at why our lovely British weather is usually the culprit and I will break down the real world costs for a professional brick spalling repair which usually sits between £12 and £26 per brick.
Spotting the Early Signs
Before you even start ringing up builders for a quote you need to know exactly what you are looking at on your own property. I always tell my clients to take a few photos so they can clearly track the brick spalling before and after the wet winter weather hits. Here is my personal checklist to help you spot the early warning signs on your outside walls before the damp spreads and creates a brick spalling interior wall nightmare.
Crumbling Faces
The most obvious sign is the surface starting to flake off. You will often notice the centre of the brick hollows out first leaving a rough pitted texture behind. If you touch the wall and powder or small pieces fall off into your hand you definitely have an active moisture problem.
Cracking Mortar
Have a really close look at the joints between the bricks. If the mortar is cracking or chipping it leaves the edges of your bricks totally exposed and vulnerable to the rain.
Efflorescence:
This is a chalky white powdery substance that appears across the surface of the brickwork. It does not cause the bricks to blow directly but it is a massive clue proving that significant moisture is moving right through the wall.
Why Do Bricks Spall in the UK?
Let us talk about the main reasons your walls are crumbling. After years on the tools I can tell you it is usually a mix of our lovely weather and some poor building choices.
The Freeze Thaw Cycle
Clay bricks are naturally porous which means they absorb rainwater just like a sponge. When our brutal British winters arrive and temperatures drop below zero the water trapped inside the brick turns into solid ice. Because water expands when it freezes the ice pushes extremely hard against the inside structure. We call this the freeze thaw cycle. As this cycle repeats over a few cold winters the outward pressure eventually blows the front face right off the brick.
Incompatible Mortar
This is a massive mistake I see almost every single week on older properties. Historically houses were built using a soft lime mortar which is highly breathable and allows moisture to escape. But over the years people have repointed those same joints using hard modern cement mortar. Cement is not breathable at all so it completely traps the moisture inside the wall. Because the water cannot escape through the mortar joints anymore it forces its way straight out through the softer brick faces instead.
The Hidden Culprits
Sometimes the bricks and the mortar are absolutely fine but they are just getting completely battered by a secondary issue. If you have leaking gutters or blocked drains overflowing directly onto your exterior walls the bricks will become constantly saturated. Another massive problem is a damaged damp proof course which allows ground moisture to constantly rise up into your lower brickwork. You must always fix these hidden culprits first before you even think about replacing any bricks.
Brick Spalling Repair Cost and Why you should not DIY IT
When I get called out to look at a crumbling wall the first thing clients ask about is the brick spalling repair cost. I see so many folks searching how to fix spalling brick without replacing hoping for a cheap weekend fix. Let me save you the hassle and the money right now.
Here is a realistic look at the numbers for a proper repair based on current UK prices.
Repair Method | Estimated UK Cost | Best For |
|---|---|---|
Single Brick Replacement | £12 to £26 per brick | £12 to £26 per brick |
Full Wall Repointing | Varies by square metre | Walls suffering from bad cement mortar. |
Warning!! Step Away from the Trowel
I know a quick surface patch sounds appealing but covering up a blown brick never lasts. You are just hiding the trapped moisture and the face will eventually fall off again. You must physically cut out and replace the damaged brick. I highly recommend leaving this to a professional. Chiselling out old masonry is incredibly tough work and if you slip you will destroy the healthy bricks right next to it causing an even bigger structural headache.
Taking the proper route means the new bricks will be bedded in fresh mortar correctly and your wall will regain its strength.
Prevention and Breathable Treatments
Once your blown bricks are replaced you need to protect that investment. Before applying any brick spalling sealant you must fix the root cause of the damp. If a broken gutter pours water down your wall the repairs are wasted money because the frost damage will just happen again. Get those leaks sorted first.
Next we look at sealing the brickwork. Please do not buy a standard masonry sealant. These form a non breathable skin over the brick. They stop rain getting in but trap all the internal moisture inside the wall causing more blown faces later. Instead you need a highly breathable masonry creme.
These creams penetrate deep into the clay creating a water repellent barrier that stops rain dead. The brilliant part is they still allow water vapour to escape so the wall can naturally breathe.
Conclusion
Catching spalling early is the absolute key to protecting your home. As a brickie I can promise you that ignoring a few blown faces today will cost you an absolute fortune in masonry bills tomorrow. Keep a close eye on your brickwork and act fast the moment you spot those early warning signs.
If your wall has suffered severe freeze thaw damage you might need more than just a quick patch job. Before you call in the builders head straight over to our Brick Calculator. You can figure out exactly how many facing bricks you need for a proper rebuild so you do not get overcharged on materials.
