Understanding Efflorescence: Causes, Prevention, and Treatment

Have you ever looked around and found your wall looks… off? The bricks are covered in a white, chalky powder, like someone dusted them with flour. 

Maybe it’s creeping across your patio slabs. Maybe it’s on your basement wall, flaking through the paint you only just finished.

Looks harmless, right? That’s efflorescence. 

And while it doesn’t destroy things overnight, it’s a warning sign. One that tells you: moisture’s moving through your walls. Salts are being dragged with it. And if you ignore it, the damage doesn’t stop at the surface.

Let’s break down what efflorescence actually is, where it comes from, how to spot it early, and—most importantly—how to stop it from ruining your walls, crumbling concrete, and damaging brickwork or render.

What Is Efflorescence?

Efflorescence is the white, powdery deposit you see on brick, concrete, render, or stone. It’s not paint. Not mould. Not mildew. It’s salt. Mineral salts are left behind after water has moved through a wall or surface and evaporated on the outside.

Water goes in, picks up salts from inside the material, and then escapes through the surface. When it evaporates, it dumps those salts on the outer layer.

That’s what you’re seeing.

What Causes Efflorescence?

Efflorescence needs three things to show up:

1. Water-soluble salts – found naturally in bricks, concrete, plaster, and mortar.
   
2. Moisture – rain, groundwater, leaks, condensation—it doesn’t matter how.
   
3. A way out – a path for that moisture to travel to the surface and evaporate.
   

Remove one of the three, and efflorescence can’t happen.

Now, let’s look at where these usually come from in a home.

Common Places You’ll Find Efflorescence

Brick Walls (Especially Newly Built Ones)

Fresh brickwork is notorious for showing efflorescence within the first year. Why? Because the bricks and mortar are still drying out. If it rained during the build or bricks weren’t stored properly, the salts get activated and pushed out fast.

You might spot it more after a wet winter, especially if your wall doesn’t get much sun.

Concrete Surfaces (Steps, Slabs, Driveways)

Concrete loves to hold moisture. And it’s full of calcium salts. Rain or rising damp from the ground beneath can push salts to the top. You’ll often see this in cold spots, under planters, or where drainage is poor.

Painted Internal Walls

White streaks showing up under flaking paint? That’s often efflorescence pushing through from damp brick or plaster behind. It’s trying to get out, and the paint’s in its way.

Basements and Retaining Walls

These sit up against damp soil. If there’s no proper tanking or waterproofing, water seeps through slowly and brings salts with it.

Efflorescence vs Mould vs Lime Bloom

It’s easy to mix these up, but they’re not the same:

👉 Related Blog: How to Cure Rising Damp in an Old House

Surface Problem	Looks Like	Caused By	Fix
Efflorescence	White powder	Salts in damp brick/concrete	Remove salts + stop moisture
Mould	Fuzzy, black or green patches	Humidity, condensation	Kill mould + improve ventilation
Lime Bloom (on concrete)	Pale cloudiness	Lime reacting with CO₂	Often fades with time

Signs That Point to Bigger Problems

Efflorescence isn’t dangerous on its own. But it rarely turns up without backup. If you’re seeing it regularly, there’s moisture involved—and that’s where the real trouble starts.

Look for:

• Bubbling or flaking paint
  
• Crumbling plaster or render
  
• Damp patches that don’t dry
  
• Mould forming in corners
  
• Musty smells near affected areas
  

These signs suggest the wall isn’t just drying out—it’s staying damp. And that can cause dry rot, mould, and long-term structural damage.

How to Get Rid of Efflorescence (The Right Way)

Step 1: Dry It Out

Before you start cleaning, stop the source of moisture. If water’s still seeping in, the salts will keep coming back no matter how many times you scrub.

Check for:

• Leaking gutters or downpipes
  
• Cracked pointing or rendering
  
• Rising damp (check if DPC is breached or missing)
  
• Bridged damp-proof course (e.g. soil or decking above DPC)
  
• Basement water pressure (look for lateral damp)
  

Fix these first.

Step 2: Brush It Off

Once the area is dry, use a stiff brush to remove the powder. No water, no chemicals. Just a dry brush.

Why? Because water activates more salts. Wet scrubbing often makes things worse.

Do it gently. You don’t want to scuff the brick or push salts deeper.

Step 3: Clean With Acid (Only If Needed)

Still not gone? You can use a mild acid cleaner like diluted white vinegar or a proprietary brick cleaner (read the label—some are too strong for softer bricks).

Apply with a sponge or low-pressure spray. Let it sit briefly, then rinse thoroughly. Never use a power washer—it drives water and salts deeper into the wall.

Preventing Efflorescence for Good

You can’t remove all salts from brick or concrete. But you can stop the moisture that brings them out.

1. Improve Drainage Around the Building

Efflorescence often starts with poor drainage. Make sure:

• Gutters and downpipes work and don’t spill water down the walls.
  
• Ground slopes away from the house, not toward it.
  
• Patio or driveway doesn’t pool water near your foundations.
  
• French drains or soakaways move water away properly.
  

2. Repoint and Repair Damaged Masonry

Gaps in mortar joints or cracked render give water a path in. Repoint with the right mortar for your brick (especially if you’ve got soft Victorian stock).

Avoid hard cement mortar on old bricks—it traps moisture and makes problems worse.

3. Protect New Brickwork From Rain

Building an extension or repointing a wall? Cover it during wet weather. Bricks soak up water fast during building work, especially if left uncovered.

Once dry, you can apply a breathable masonry water repellent—but only if you’re sure the wall is dry and well-pointed.

Avoid clear sealants that trap water inside.

4. Treat Rising Damp (If That’s the Cause)

If efflorescence shows up near ground level, rising damp might be to blame. Look for:

• Salt lines on the bottom of the walls
  
• Plaster “blowing” or crumbling low down
  
• Tiled or wooden floors lifting or warping
  

You may need a chemical DPC injection or to replace the damp-proof course entirely. This isn’t a DIY job—call a damp specialist.

👉 Related Blog: How to Treat Rising Damp: A Complete Guide for UK Homeowners

Internal Efflorescence—When It’s Inside the House

Efflorescence on internal walls is a sign that something’s gone very wrong behind the scenes. It usually means:

• Water is seeping through the external wall
  
• The cavity is bridged (e.g. rubble or insulation holding moisture)
  
• Internal plaster is drawing moisture from the brick
  

You’ll often spot:

• White streaks under flaking paint
  
• Powder pushing through under the wallpaper
  
• Damp smells or mould nearby
  

Fixing this means removing the plaster, drying the wall properly, and fixing the external issue. Then re-plaster with breathable materials like lime or renovating plaster.

When Efflorescence Turns Into Spalling

Here’s where things get ugly.

If salts build up under the surface and don’t escape fast enough, they expand. That expansion can pop bits of the brick face off, called spalling. It’s especially common in frost-prone areas.

Once bricks start crumbling, there’s no patching them. You’ll need to cut out and replace the damaged ones.

Don’t ignore flaking bricks. It means the wall is absorbing water, and it’ll only get worse.

When to Call in a Pro

Call a damp or masonry specialist if:

• Efflorescence keeps coming back after cleaning
  
• Internal plaster is crumbling or lifting
  
• You suspect rising damp or cavity bridging
  
• Bricks are flaking or crumbling (spalling)
  
• The affected area is large or in a basement
  

Ask for a proper damp survey—not just a builder’s guess. You need to know if the issue is surface-level or structural.

Final Thoughts

Efflorescence is your home’s way of saying, “There’s moisture here—and it’s moving.”

It might look like a minor cosmetic issue, but it’s a red flag for deeper damp problems. Catch it early, and it’s a cleanup. Leave it too long, and you’re replacing bricks, plaster, and potentially footing a structural repair bill.

Look after your brickwork. Watch for the signs. And when white powder shows up? Don’t just brush it off and walk away.

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