Substrate preparation

Whether you’re fixing ceramics, porcelain, mosaics or natural stone, preparing the surface correctly will ensure a professional and lasting finish for your tiles. If the surface isn’t correctly prepared it can lead to problems further on like tile failure, cracking and the need for retiling.

Tiles can be fixed to most walls as long as they are properly prepared. The walls must suitably level, clean, dry, and free of dust, grease or any loose material. All surfaces must be completely secure without any obvious movement and capable of carrying the additional weight of the tiles and adhesive.

When tiling onto walls, consideration must be given to weight of the tiles. Our store teams will be happy to confirm the weight of the tiles so you can confirm suitability. Please include 3KG per m² in your calculation to allow for the weight of the adhesive and grout.

Walls have a maximum tiling weight depending on the surface being tiled onto, if your tiles, adhesive and grout together exceed this weight capacity a tiler backer board should be used. Guidance weights are:

Gypsum Plaster – up to 20kg/m2

Gypsum Plasterboard – direct without a plaster skim up to 32kg/m2

XPS Boards (wedi) – up to 120kg/m2

Cement Boards (HardieBacker) – up to 200kg/m2

Always check the manufacturer’s guidelines on weights and installation process.

Before tiling or levelling, certain substrates require priming. Priming reduces the porosity (absorbency) of substrates and prevents the formation of air bubbles or pinholes.

Priming is an essential step prior to tiling, it adds strength to weak surfaces and also minimises the risk of chemical reaction with cement-based adhesives.

Always refer to the manufacturer’s guidelines when choosing your primer as different substrates have different priming requirements. These guidelines will also denote how to use your primer, whether it’s diluted or undiluted, mixing ratios and the number of coats required.

Ensure the surface is clean, dry and free from dust, grease and any other contaminants that could affect adhesion before applying your primer.

Maximum weight loading 20kg/m2. Bare Plasterboard – maximum weight loading 32kg/m2.

New backing coat and skim coat plaster must be allowed to dry for at least 4 weeks prior to tiling. New plaster skim coat on top of plaster board must be allowed to dry for at least 7 days prior to tiling.

All plaster/plasterboard surfaces should be primed, undiluted, with BAL Prime APD when using a BAL cementitious powder adhesive. If you’re using a BAL Ready Mix Adhesive then prime with BAL Prime APD diluted at 1:1 with clean water.

All surfaces must be completely dry prior to tiling.

The weight is dependent on the substrate type and the existing tile weight. Make sure the tiles are entirely clean, degreased and are firmly fixed to the wall. Any damaged or loose areas should be made good. Check that the surface to which the existing tiles are fixed will take the weight of the additional layer of tiles you are adding, this severely limits your choice of tiles so it is often best to remove any existing tiles.