Tips to prevent efflorescence during tile and stone installation

What is Efflorescence?

Have you ever noticed white deposits on the wall and floor surfaces of your tile or stone installations? This white residue is the result of efflorescence. Efflorescence is a natural occurrence in Portland cement applications. All Portland-cement based products, which are present in render and screed mortars and most cementitious adhesives, will have this presence of calcium hydroxide crystals after the hydration process. Efflorescence usually arises from the percolation of water through the cement-based backing that leaches out soluble salts, which are then deposited on the surface through the joints. The leached lime, when exposed to the atmosphere, will react with carbon dioxide to form calcium hydroxide crystals. To put it simply, the presence of water, travelled through a water path in contact with the calcium salts present in cement-based products, is drawn out to the surface through the capillary pores of the cementitious tile grout. Once the water evaporates, it leaves behind a white residue. Efflorescence is harmless, but unsightly, and can occur on both vertical and horizontal surfaces.

Efflorescence in tiles and stone stairs flooring

What causes Efflorescence?

A combination of three factors cause efflorescence:

Soluble salts present in cementitious mortars, i.e., leveling mortars, adhesive bed and tile grouts.
Water
Water path (passage for water to travel).

Typical site conditions that can trigger efflorescence:

Excessive damp and humid environments (water feature, swimming pool)
Use of excessive water and methods in wiping off surplus grout when cleaning tile joints
Outdoor areas that are exposed to rain and potential water elements and are not protected
Prolonged delay in drying out after complete tile installation
Joints are too narrow and difficult to properly fill it with grout mortar

Efflorescence in narrow joints

Preventive measures

To totally eliminate efflorescence in the tiling system, tile/stone installations should be free of cementitious mortars. However, it is not always possible as cement-based products are normally needed for levelling beds (i.e. renders and screeds).

Hence, it would be better to eliminate any one of the above three conditions to prevent efflorescence. Let’s take a look at the preventive measures:

For external flooring applications, it is important to ensure that the tile joints are filled as soon as possible during works in progress. Otherwise, provide “shelter” to protect the “open” joints from rain and water after the tiles have been laid.
Incorporate a waterproofing barrier (e.g. flexible cementitious waterproofing mortar) over the entire levelling beds before laying tile with tile adhesive.
Use epoxy or polyurethane-based adhesives to install tile/stone. If it is not possible, an alternative is to use fast-setting cementitious adhesives. Mapei’s Granirapid and Elastorapid cement-based adhesives contain lower content of Portland-cement in its formulation.
Allowing the substrate to cure completely and dry out before proceeding with tile installation.
Incorporate a wider joint gap between tiles so that joints can be properly grouted to sufficient depth (check out our video guide on installing tile grout).

When efflorescence have already occurred, it would require repeated washing until the calcium salt is depleted.

Contact Mapei Singapore for your project needs.

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About Mapei:

Founded in Milan since 1937, Mapei is today a world leading building material supplier of adhesives and complementary products for the laying of all types of floor, wall and coating materials. Mapei’s specialty lies in products for ceramics and stone materials, among other product lines. Mapei’s adhesives for tiles and stones are certified according to international standards and are SGBC certified. Experience proven by numerous notable projects worldwide.