Tips & Tricks


Efflorescence. What is it? How does it affect your building? Is it bad and what do you need to do about it?

I’m Matt Cornell from Cornell Engineers. Let’s have a chat about efflorescence and what it means for your building.

Efflorescence is that salty substance that appears on walls and slabs and sometimes even ceilings -that is a sign of moisture coming through the surface.

By itself, it isn’t a structural defect but it’s a sign that something’s going on that needs further investigation and that your building needs some help.

So if we have a look at a couple of these photos, you can see that¬†there’s blockwork, and salt coming through on the wall.

The wall itself is discolored in place – it’s a little bit darker around where the salt is located.

That’s part of the sign that you know that there’s moisture coming through.

So efflorescence is actually the salt that is left on the surface after moisture migrates through your cementitious or blockwork or brickwork surface.

The moisture dissolves salts out of the brickwork or blockwork or concrete and when the moisture comes to the surface the moisture evaporates leaving behind the salt crystals.

So it means there’s moisture coming through your surface and that means there’s moisture on the other side of the surface that needs to be handled, addressed and that problem solved.

Now again, efflorescence by itself is not a defect. It’s not a problem. It’s a sign of a problem.

It’s a sign, generally, of a moisture problem and that means you need to find that moisture and solve that problem.

When we look at what that looks like on paper in a wall, if we use a concrete measuring wall for example, and it might even be say a retaining wall where we know that there’s dirt on the other side of the wall when we’re standing on the inside and if there’s efflorescence on that surface then that’s a good sign that moisture is coming through the blockwork wall evaporating on the inside of the surface and leaving those salt crystals.

So you as the owner or the occupier or the person in charge of the maintenance for that building now you know that you need to go onto the other side of the wall find out where that moisture is coming from and solve that issue.

So we’ve already done quite a long video on solving drainage issues on houses on sloping sites and this ties in nicely to that in that moisture problem is going to be solved by doing some of those things in that video.

Once that solution has been attempted then it’s time to do some cleaning – take the efflorescence off the wall.

There are some quite good products that you can buy from hardware shops to dissolve efflorescence and take it off walls and surfaces and then wait to see if the¬†efflorescence reappears – after you’ve solved the moisture issue. So, solve the moisture issue first.

Clean the efflorescence.

See if it comes back. If it comes back you’ve still got some more work to do – still got some moisture issues.

Now the other issues related to moisture coming into a building are the same things that we spoke about in the other video.

That steel reinforcement, for example, corrodes when it comes into contact with moisture.

The other things are leaks, the rot of timber, and mold.

So the moisture that’s coming through and causing leaving efflorescence could also be causing mold. And finally, uneven soil moisture conditions can cause house movement and damage and we cover that on our website.

So efflorescence. Not a problem itself but a sign that your building needs some help.

I’m Matt Cornell from Cornell Engineers.