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What is efflorescence?
Efflorescence is the spread of white residue on the surface of masonry building materials, such as: bricks, tiles, concrete and stone, following exposure to water.
Where you can see efflorescence
Efflorescence can affect masonry surfaces that are indoors and outdoors. Other than the common masonry surfaces listed above you can find efflorescence on surfaces like sandstone paving, natural stone pavings and basement walls.
What causes efflorescence?
Many masonry materials naturally contain soluble minerals, such as salts. When these masonry materials become saturated with water, their salts dissolve.
The water, carrying these dissolved salts, then migrates through the porous masonry structure, reaching the surface.
When the water leaves the surface through evaporation, the salts are left behind as a white, crystalline residue known as efflorescence.
Is efflorescence a problem?
Yes. Efflorescence is on one hand a cosmetic issue; streaks or patches of efflorescence on building facades are unsightly, but they also damage the pores of the masonry. Efflorescence is a symptom of other types of water damage as well.
By the time you see efflorescence, water would have started doing damage within the structure.
In these tiles pictured below for example, the repeated influx of water has led to the growth of salt crystals underneath the tiles, and in some areas algae has grown as well. These growths have dislodged the tiles and damaged the tile bed.
On the wall below, the render has been stained and cracked. The grout has eroded as well. Within the structure, there are potentially other critical issues like rust, structural movement and more.
You can see within the blackened area, that the concrete has split apart. This has most likely been caused by the expansion of saline crystals or rusting rebar within the concrete. Rust-coloured residue has streaked down the wall below, indicating that the structure within could be rusting. The tiles themselves are dislodged and drummy.
The repeating cycle of wetting and drying the masonry does its own form of damage. As the salts move through the masonry substrate to the surface, they accumulate as crystals within the microscopic pores of the masonry as well as on the exterior surfaces.
Eventually, the pores become overloaded and break apart as the crystals grow and expand. A similar effect is often also seen in concrete structures, where the steel rebar within the concrete rusts and expands, then dislodges the concrete around it.
Efflorescence is a sign to start a repair job. If you carry out the treatment below, you will avoid cosmetic and structural deterioration of your building. We recommend this as a prevention and a cure.
How to remove and prevent efflorescence
The most important way to stop efflorescence is to prevent the ingress of water. If efflorescence is already built up, it will need to be removed first before the treatment can begin. It will be possible to remove some efflorescence from the surface, but more extreme cases will not be removable.
Some removal tips to keep in mind:
- The standard removal process is through abrasion. A brush can be used to remove the less resilient crystals. Brush with added sand for extra abrasiveness, and make the sand damp for even more.
- It is not recommended to wash or pressure wash the surface as this is adding more water to the substrate. Specialised liquid formulations are available, including acids which will dissolve the residue. This can work on hardened efflorescence.
Once the efflorescence is removed, you are ready to waterproof the surface.
Sealing masonry surfaces
The best protection against efflorescence and water damage is to use a penetrating sealer to make the surface entirely waterproof. The products we recommend using are a masonry sealer such as Resistain or Shower Plug. Both will waterproof any masonry substrate, but Resistain is a stain-proof sealer that has the added feature of stain-resistance.
Penetrating waterproof sealants are liquid solutions that repel water from masonry. Resistain and Shower Plug are brush-on waterproof sealants that can be applied using a brush, roller or spray. When applied to a clean, dry masonry surface, the penetrating sealer will soak in, bind there and create an electro-chemical barrier that repels water for decades.
Once applied, the surface will become impermeable to water, and if treated with Resistain, will also be protected against all forms of stains. Any water already in or beneath the surface will dry out.
The extent of the water damage problem along the tiled area. Applying a penetrating sealer to this surface when it was originally laid would have protected the entire surface for decades, avoiding damage and repairs later on. An unsealed surface is guaranteed to experience water damage over time.
For an easy way to learn how to apply a masonry sealer like Shower Plug, our handy guide can help you through the process and this will seal your surface for 10 years.
Prevent efflorescence and protect masonry surfaces
Shower Plug and Resistain are high-grade penetrating sealers designed to give buildings long-term protection and reduce the cost of maintenance.
Resistain can be ordered online here, and Shower Plug is available at Bunnings Warehouse (within Australia).