How to fix and stop efflorescence on verandah concrete?

Jills

Hi all! 
A couple of months ago, we had cleaned and sealed our undercover verandah concrete. This week, we’ve noticed this white powdery stuff coming up in a couple of places near our house brick walls. We can’t see any moisture coming out of the concrete / brick walls so we’re very puzzled as to why it’s there. Hoping someone here could give us advice as to how to manage this as we really want to preserve our verandah concrete. 

I’ve attached a photo below. The light brown metal you see is one of the post of the verandah structure (not a down pipe)

JacobZ

Hi @Jills,

To remove efflorescence from your sealed concrete, the best approach is to regularly clean the surface using dry methods or light detergents. 

Start by brushing the affected areas with a stiff-bristle broom or scrubbing brush to remove the powdery salt deposits. This should be done without water, as adding moisture can dissolve the salts and allow them to reabsorb into the concrete surface, only to reappear later.

If you have to use a liquid and a cleaner, use something like this Gerni Concrete And Stone Cleaner and wash it off with fresh water as soon as possible.

It’s important to note that acid-based cleaners, which are often recommended for efflorescence on unsealed surfaces, should not be used in your case. These products can damage or strip the sealer you’ve applied, potentially leading to a patchy finish or weakening the protection on the concrete. Since the sealer forms a barrier, using harsh chemicals could compromise its integrity and create more problems than it solves.

Given these limitations, your most practical option is to continue with regular brushing and surface cleaning as needed. 

Efflorescence often reduces over time as the available salts in the concrete and surrounding materials are gradually depleted. 

While it might take a bit of patience, this gentle maintenance approach is the safest and most effective way to manage efflorescence on sealed concrete.

Let me know if you have any further questions.

Jacob