Tiling uneven surfaces

A serrated adhesive spreading trowel, when used at a constant angle, enables the even distribution of adhesive onto the substrate. If the tiles are all bedded with a similar force they should be at the same height with only minimal unevenness. However, if the substrate is not level, this is much more difficult to achieve and there is more chance that some edges will be standing proud.

Localised deep holes may result in a bed thickness that exceeds the specification for a thin-bed adhesive.

Patching such holes can be time consuming if there are more than a few of them.

In some instances, for example when tiling over a layer of existing ceramic tiles, the above mentioned problems may be combined.

Some tiles may need to be removed because they are unsound, whilst others may have been imperfectly fixed and exhibit some variation in height.

Uncalibrated natural stones are stones that have been split along natural fracture planes rather than machine cut. The result is a stone that varies in thickness, both from within each stone and from piece to piece. These types of stones require an adhesive that can be applied to greater thickness than normal.

There are a number of possible solutions depending on the condition of the substrate. A levelling compound will give a smooth surface but this does not help with uncalibrated stone where a high-build adhesive must be used. Deep holes should be filled first with a repair mortar.