Case 1

Cause of Defects

For cement-based substrates like concrete and the render layer, leaching out of soluble salts/lime from the substrate’s pores or cracks will be deposited on the tiled surface through the tile joints. The leached lime (calcium hydroxide) will react with carbon dioxide present in the atmosphere to form calcium carbonate crystals (lime bloom) on the surface of the façade. While lime bloom is a thin layer deposit, another form of efflorescence known as lime weeping is a build up of calcium carbonate to form thick encrustation [1].

For clay bricks substrates, the salts are normally sulphate and chloride salts which can originate from the mix or migrated from an external source. The efflorescence is normally in the form of fluffy deposits.

Water can enter the tile system via a number of ways:

Cracks on the tile surface/ delaminated tiles 

Cracks on the tile surface or delaminated tiles provide an avenue for water to seep into the backing. Leaching out of soluble salts from the backing would hence be able to appear on the tile surfaces similarly.

Faulty tile joints 

Another point of water entry can be through the joints of the tiles. Lack of adhesion and cracks in the mortar joints results in voids which water can seep through. A poor mix of the mortar or adhesive used for jointing will also result in porous joints.

Porous tiles

A wrong choice of tile material is common especially if the designer did not consider the tropical conditions in which they are to be fixed. Some tiles might not be durable enough to withstand the weathering effects of Singapore and might be too porous to be used locally although they might be widely effective from the origin of import.

Poor quality of materials

The cement and sand used for the render, tile bed and substrate might consist of a high content of impurities such as soluble salts.