Efflorescence
What is efflorescence?
Efflorescence is the process by which salt migrates to the surface of a porous material, forming a coating of crystalline salt deposits (also called Calcium Carbonate or limestone). The appearance of efflorescence is often described as a white, fluffy or powdery substance, but it can range in colour from white to grey, brown, or even yellowish hues, depending on the type of salts present. This can be an aesthetic concern. To identify efflorescence, look at the brickwork on walls, masonry walls, or concrete surfaces, it occurs when water evaporates and leaves behind salt deposits on the masonry which are brought to the surface. Water, rain and snow are the primary sources of moisture and may impact the degree of efflorescence.
Efflorescence can occur at different times. It can either be a problem from the beginning of a building’s construction or occur over time. Primary efflorescence can appear within the first 72 hours of the building materials being used, where excess moisture is present. Secondary efflorescence is due to external moisture issues and water penetration, which extracts salts to the surface of the building materials.
Installation problems which may lead to efflorescence:
- Using construction materials that are not fit for purpose or of poor quality, these salts can easily migrate to the surface
- Improper ground storage of building material, for example, damp soil or ground moisture
- Use of masonry without sufficient ventilation
- Use of masonry in areas that lack a proper moisture barrier
- Joint material failure
- Improper construction techniques could lead to structural damage
- Environmental factors and climatic conditions include high humidity, heavy rainfall, and frequent freeze-thaw cycles.
How to troubleshoot efflorescence
- Assess the affected structure: is the building old or new, how old is the brick wall
- Check out the building material condition i.e cracks that could lead to efflorescence (calcium carbonate)
- Observe the location of efflorescence to determine the water source
- Check masonry surfaces for moisture and any possible sources of contamination by water soluble salts
- Consider other external water sources i.e condensation within a wall, faulty drain pipes
Preventing efflorescence
While it is difficult to completely prevent salt efflorescence, good site practice will help to minimise the occurrence.
- Properly cure concrete after it has been poured, this will help prevent the formation of salt efflorescence
- Bricks should not be placed directly on the ground to prevent water from getting into the materials
- Mortar should be protected from damp contamination and moisture
- Mortar that is not cleaned may lead to salt efflorescence(salt deposits)
- Newly built brickwork should be protected from the elements in the first week to prevent salt efflorescence
How to remove efflorescence
Efflorescence is temporary. In most cases it will disappear in a few wet winter months in this country, therefore the best solution is often to let it wash out naturally. However, there are some tips for efflorescence removal effectively.
- When treating an outdoor wall, make sure the temperatures will be above freezing all-day
- Simple washing can sometimes remove brick efflorescence
- Scrub the affected area with a wet sponge or brush and plain water. Always rinse thoroughly; if you leave dissolved salts on the surface, they’ll return with new efflorescence.
- Watch out for clay. Clay naturally has a high salt content, so removing efflorescence in this way is often only a temporary solution—wet weather can bring salt back to the surface again.
- A stiff scrubbing brush and a dry brushing technique will remove the efflorescence.
- Muriatic acid can be used for efflorescence removal, but it poses risks such as discolouration and potential surface damage. Consider safer commercial solutions.
If efflorescence is causing you problems, contact us for expert advice.
