Weber Saint-Gobain - Official website of the company

Substrate preparation

When the substrate is cement or ceramic based, its strength cohesion should be checked before tiling. Check for voids and weak points using a hammer. Hollow sounds indicate that the

substrate is weak and poor in adherence. In such cases, it is necessary to identify the hollow area and to work on it again for a better adherence using a new mortar or new similar tiles.

When the substrate is painted, the adhesion square test should be performed. Draw small squares 2x2 mm, with a sharp knife on a surface of 10x10 cm. If 80% of squares stay fixed to the substrate, the paint has good adhesion and new covering can be directly fixed using the recommended tile adhesive. In some situations, like tiling on gypsum boards, it may be necessary to prime the substrate to increase adhesion.


The substrate must always be clean, free from dust, oils, paints or any other substance that decreases the adhesion of the tile adhesive. In concrete substrates, the remains of demolding oils, surface water repellents products, or low resistance surface concrete should be removed. This can be done with high pressure water jet, sandblasting or brushing.


Substrate must be completely dry before being covered. Cement based substrates shall have a moisture level not exceeding 10% before covering. Gypsum based substrates should not

have moisture higher than 3%. Check that there is no rising in humidity by capillary action. In

such a case, specific waterproofing treatment is needed, before applying the tile adhesive over the substrate.

Type of joints

The coverings are subjected to many stresses as a result of temperature and humidity changes,

as well as the loads and strains that the structure has to withstand. To avoid debonding of

tiles, plan and use joints between the tiles to decrease or absorb these stresses.

When fixing ceramic or natural stone tiles, or other covering material, the use of joints should

always be considered between tiles, floors and walls.