Achieving a suitable adhesive bed

The adhesive bed performs a number of functions: it sticks the tile to the surface; it absorbs differential movement between the substrate and the tiles; it protects the substrate from water; it absorbs deflections; it enables the tiler to adjust the height of each tile; it accommodates limited errors in the substrate. There are a number of ways that an improper adhesive bed can cause problems in the life of the installation, as detailed below.

Common issues and queries you can face

Water that may penetrate the grout

Voids behind the tiles allow access to any water that penetrates the grout which can cause:

  • A damp musty smell in showers
  • Water leaks can be made worse
  • Trapped water to freeze and expansion can push the tiles off



Floors susceptible to point loads

Ceramic tiles are inherently brittle and therefore any area of the tile that is not fully supported is vulnerable when subjected to a localised load. Examples could be: a chair leg, something being dropped, or any heavy item on small feet such as a kitchen appliance.

Thickness of the adhesive bed is also important

  • If the bed is too thin a cement-based adhesive may dry out very quickly and not gain strength.
  • In the case of floors where some movement is expected the adhesive is required to give and its ability to do this is severely limited if it is applied too thinly.

Adhesive bed will show through some tiles

  • Some tiles and natural stones (e.g. limestone and marble) will show a shadow on the face where the adhesive is in contact behind. Voids will be visible from the front of the tiles.
  • Areas where there is no contact between the tile and the adhesive bed will not be bonded. A 50% contact will therefore result in only 50% of the overall bond strength across the tile.