Freshly plastered walls and newly screeded floors should be treated to a coat or two of PVA when the plaster/screed is completely dry and before laying tiles.

Painted walls should be degreased and free of surface contaminants. Where there are already tiles on the wall but these are being replaced, it is important to remove every trace of tile, grout and adhesive. The surfaces should be level and this may require getting a professional plasterer to skim over the existing surface to achieve a smooth, even finish.