What Is Efflorescence

First Published: 2 November 2014 | Updated: 24 April 2024

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Efflorescence’ is the term most commonly used to describe the deposit of crusty white mineral salts that appear on a masonry surface (concrete, render, brick or mortar) that have leached out from within the substrate when moisture migrates through it.

Efflorescence in masonry appears as white alkaline salts on the surface and consists mainly of calcium carbonate. A reasonable amount of moisture is required for it to form

It should be recognised that there must be water (moisture) present to dissolve and/or transport these salts so the source of the moisture needs to be either blocked (if it’s external to the substrate, such as groundwater) or exhausted (if moisture is emanating from within the substrate, such as rising damp).

Soluble salts can be introduced to your masonry product in a number of different ways. They can be found externally in the fill, soil or sand surrounding the product or brought in by the environment such as sea spray. Occasionally the soluble salts can be found in mortar, grout, dried sweeping sand and even the masonry units themselves.

It is always recommended that a good quality washed bedding sand be used under your pavers to help minimise the presence of soluble salts. As the name suggest washed sand has been washed to remove a lot of the finer material which also removes any of the salts that may be present.

Although efflorescence looks unsightly and aesthetically displeasing it does not affect the product if dealt with quickly and correctly.

Efflorescence can easily be removed with a few steps. It will also generally disappear over time but the process can be accelerated by dry brushing off any residue and removing it from the site by either a dustpan or vacuum cleaner before scrubbing with a brush and clean water. If the salts are not removed from the site they will just be reabsorbed into the masonry product when washed down. Repeat the process until the problem has stopped.