How to Clean Efflorescence And Stop it Coming Back

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Have you ever seen growth on one of your stone walls or floors that looks like an off-white salty powder, quite hard and calcified? This growth is efflorescence. In this article, you’ll learn all about efflorescence and, yes, how to prevent it.

What is Efflorescence?

We live in a time when pressure to build quickly is on us. New products are being developed to assist with this required pace, and although they can certainly help with speed, there is usually a side effect. Efflorescence is such a side effect of speed!

Previously, builders would use grey cement for cementitious substrates. Sand cement screed, render, concrete are all examples.  

There is a curing process required of up to 5 days before waterproofing, tiles or paint could be applied to the surface.


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Then along came off-white cement, which actually has a green colour to it. This off-white cement has an increased Lyme content, used to speeds up the dry time to reduce build time. Work is not delayed by dry time and can continue as scheduled. That takes worries about potential rain off the builder and enables the new homeowner to move in earlier. 

The problems arise later. Houses move. This movement causes tiny hairline cracks, that allows water and oxygen to penetrate the cementitious substrate. When the water later evaporates from the substrate, Lyme scale, a mineral similar to salt, is left on the surface.  It is actually a powder, but exposure to the sun and other chemicals hardens or calcifies it. This mix can be extremely difficult to remove.

You may also find small amounts of efflorescence in buildings where off-white cement was not used.  Increased Lyme content is a requirement for efflorescence. This Lyme content could  be in the sand or other building materials if they are not washed or are of lower quality. It can even be in the water used mixing building materials, although this is unlikely in most areas. But the content is usually too small to cause unsightly calcification.

Efflorescence is not inherently harmful. Cracks must exist first in order for the efflorescence to occur, not the other way around. Movement is responsible for these cracks and these cracks enable water ingress, that also may cause internal damage to structural components over time.

Efflorescence is a symptom, not the cause, of water ingress.  Efflorescence is water-soluble, but does not evaporate when water changes from a liquid to a gas or water vapour and remains on the surface. It can cover up a crack, but rest assured it is there.

And you may not see any evidence of a crack until you clean up the efflorescence. While efflorescence in itself is mainly an aesthetic issue, Lyme is super porous and absorbs water.

So it’s not dangerous, but it sure is ugly!


How Does Efflorescence Form On Stone Surfaces?

Stone or concrete surfaces are more porous than ceramic or porcelain tiled surfaces. Therefore, they will allow more water transfer, which will increase the effects of efflorescence or speed it up if no waterproofing is installed on top of the screed or the screed is damaged.

Efflorescence can occur indoors and outdoors, although it is predominantly an external issue.  The impact of evaporation is stronger outside and external surfaces are more frequently subject to wet conditions than indoor surfaces, where spills get cleaned up fairly quickly. Efflorescence occurs across the world in any temperature and environment. To have efflorescence occur, the follow criteria must be met:
  • Water-soluble salts/Lyme content are present within the substrate.
  • Movement cracks must occur, or
  • Moisture has access which causes the salts to dissolve
  • Water is drawn to the surface taking water soluble salts to the surface. As water turns into vapour as part of the evaporation process. The salts crystallise, which is what we call efflorescence.
Rain, snow, or any water at all are the key moisture sources that might influence the extent of this salty issue. Interior activities, groundwater wicking, and condensation can all have an impact on moisture creation.

There are various stages where the staining will take place. It might be an issue from the start of a construction project, or the problem may develop through time. Initial efflorescence generally appears during the first 28 days of cracks appearing, these cracks are usually due to movement allowing water access to the substrate. Evaporation pulls water moisture to the surface then turns it into vapour which as a gas will not contain soluble salts leaving them on the surface.

The horrid chalky stains could indeed emerge whenever construction materials get fitted poorly or if installation issues arise. Here are some typical examples:

What Are The Effects Of Efflorescence If Left Untreated?

Unlike mould, this off-white formation is harmless, which means that it won’t hurt you, however, it is ugly. It can theoretically be left undisturbed since it provides no health risk. But, it should be addressed as promptly as practicable since it shows that water has access to the substrate and water damage can occur. If the waterproofing membrane is installed on top of the substrate but below the screed you might have efflorescence and not water damage as water has access to the screed but the membrane is protecting it from travelling further down. But if the membrane is installed on top of the screed and you are seeing excessive amounts of efflorescence you can be certain that your membrane has failed.

Can Efflorescence Be Cleaned Off?

Most certainly! Efflorescence is just a water soluble mineral, usually lyme that is left deposited on the surface when water from the substrate is evaporated. Then over time it is calcified due to exposure to the sun and other minerals. But it is key to know that it is a deposit and just like when you deposit $10 in the bank you can withdraw it. Same goes for efflorescence: it is on top of the surface so it can be removed and the surface will be like it was before it occurred.


How To Clean Efflorescence

Hydrochloric acid eats efflorescence. Wet the surface down first so that the acid is not absorbed into either the tile if it is concrete or stone or grout as it will bleach the pigmented grout. Then wearing the correct Personal Protective Equipment including glasses for the eyes, mask including vapour filters, gloves and adequate clothing and footwear. Pour pure hydrochloric acid that you get from the hardware to where the efflorescence is. If the acid does not react with the efflorescence then you may need to disturb the surface as it has probably calcified. This can be done by hitting it with a bolster. Continue to reapply or reactivate the acid by scrubbing over the efflorescence with a wire brush as seen in this video. Continue to clean down until the efflorescence is removed and sufficiently dilute the acid with water to ensure that it does not continue to react with other materials and keep out of water ways.

Why Does Efflorescence Keep Coming Back After Cleaning?

Efflorescence occurs due to water being able to access the substrate where increased lyme content is. When you use water to clean the efflorescence you have provided the necessary materials in order for it to re-occur. Yes efflorescence is on a time lock. The water that you use for cleaning will create further efflorescence in 14-28 days.


How to Prevent Efflorescence from Coming Back

To prevent efflorescence coming back or out you must prevent water going in. Applying Remedial Membranes Clear Waterproofing Membrane over the tile creates a continuous waterproofing barrier over the tiles so that water does not have access to the substrate which is key to preventing the process of efflorescence.

It is true that the water you used in cleaning the efflorescence will create new deposits in 14-28 days but as this will occur under the membrane it will remain powder-like. The membrane can be scraped back the power like efflorescence can be removed with methylated spirits (be sure not to use water otherwise the process will repeat itself) and then patch repair that section of membrane and the efflorescence will not return. Be sure to leave enough time to ensure that all the efflorescence has come to the surface but you don’t want it to break the membrane and allow water back in.

How to Use Remedial Membranes to Remove Efflorescence from Stone

The process of removing efflorescence from a ceramic or porcelain tile is essentially the same for stone or concrete. You will still use hydrochloric acid to eat away the efflorescence however because the tile is super porous you need to be mindful to ensure that surface is sufficiently wet not just before you apply the acid but during the application as stone and concrete will start absorbing the water initially applied which will encourage the acid to be absorbed as well this will result in the stone or concrete being bleached. To ensure this doesn’t happen ensure that you have water available and add it to the area as you start seeing signs that water is being drawn away.

Benefits of Using Remedial Membranes for Removing Efflorescence

By installing the Clear Waterproofing Membrane and patch repairing the sections when efflorescence occurs after 14-28 days of the initial application and preventing water ingress you have effectively halted the chain reaction process, which will stop this annoyance from recurring.You have you balcony, shower, facade back looking like new and the way it was designed.


Off White Cement should not be used in any aspect of the building to avoid efflorescence. But for those whose building is already built and it is too late and efflorescence is present. Using the Clear Waterproofing Membrane over the surface will prevent efflorescence from reoccurring.