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The term efflorescence is used to describe the chalky white mineral deposits which sometime form on the surface of masonry surfaces (concrete, render, brick or mortar). It can be a cosmetic issue, or it can be an indication of moisture intrusion in the substrate, which could lead to major structural and indoor air quality, issues.
Indications of Moisture
Efflorescence (which means "to flower out" in French) is the dissolved salts deposited on the surface of a porous material (such as concrete or brick). Porous materials can absorb and wick water through a process known as capillary action; as the water moves through the material and finds its way to the surface it evaporates leaving behind the white powdery looking salts. The moisture that creates efflorescence often comes from groundwater, but rainwater can also be the source.
Efflorescence itself does not pose a major problem, but in some cases when it continues unabated it is likely to be an indication of moisture intrusion from an external source which unaddressed can pose significant ongoing problems including moisture ingress into framing timbers, rot, and undermined structural integrity.
In new constructions efflorescence may only be a cosmetic issue, as residual moisture in the building materials dries and cures, it will naturally cease.
Efflorescence can often be confused for mould; here are a few tips to identify the differences:
- Pinched between the fingers, efflorescence will turn into a powder, while mould will not.
- Efflorescence forms on inorganic building materials, while mould forms on organic substances. However, it is possible for mould to consume dirt on brick or cement.
- Efflorescence will dissolve in water, while mould will not.
- Efflorescence is almost always white, yellow or brown, while mould can be any colour imaginable. If the substance in question is purple, pink or black, it is not efflorescence.
- If you dab a bit of the white chalk on your tongue and it's salty, it's probably efflorescence.
Prevention, Removal, and Solutions to Efflorescence
Without doubt, the best way to prevent efflorescence from occurring in the first instance is to put the following practices into effect at the design & construction phase:
- Ensure that the substrate is fully cured (at least 28-30 days for concrete and cement render / 10 weeks for fibrous or set plaster, depending on ambient conditions) prior to painting.
- Good drainage to prevent water “ponding or pooling” on horizontal surfaces.
- Wherever possible, keep masonry dry during the construction phase by covering it with plastic sheeting and storing on pallets otherwise moisture from damp soil and rain can be absorbed.
- Installation of appropriate capillary breaks (waterproofing) to effectively prevent rising, falling or lateral damp or any water ingress from an external location (such as soil), as this can activate the alkaline salts within the masonry substrate allowing these salts to be transported to the surface by moisture. E.g. the installation of polyethylene moisture barrier between the soil and building material.
- Protect bare and non-painted masonry from water intrusion by applying water repellents such as silicone solutions.
- Pressurised water can sometimes be used to remove or dissolve efflorescence; however this may result in the reabsorption of salts and they may later reappear so it is advisable that if water is used in the removal it is dried off very quickly
- Efflorescence and alkali salts can be removed by dry brushing with a stiff bristled brush followed by wet sponging the surface with a mild 5% solution of white vinegar (Acetic Acid) in water. The whole area should then be wiped down with a damp cloth and allowed to dry thoroughly.
Efflorescence is often a symptom of a bigger moisture ingress issue so it will only stop forming when the migration of moisture through the substrate stops. Unless the source of the moisture causing the efflorescence is traced and eliminated then it is highly likely that the salts will continue to reappear over time.
You may need to engage an inspector to investigate the cause of the moisture. Both rain and ground water can be sources so checks should include; subfloor drainage, downpipes, junctions in the cladding, spouting, roof flashings etc.
In summary, efflorescence is a cosmetic issue, but it indicates a potential moisture problem. Causes of moisture ingress resulting in efflorescence can vary so a thorough inspection should be undertaken and the source eliminated. The team at NZ House Surveys are qualified to carry out these investigations, if we can help give us a call today on 0800 487 884.