Tiling uneven surfaces
It is important, both for appearance and for safety, that the finished tile surface is flat with no tiles standing higher than the others. Providing the normal tiling practices are followed this is straightforward on flat, level substrates. If the substrate is not flat then a number of problems can arise.
1. Increased difficulty in achieving a flat finished surface on the tiles
A notched trowel, used at a constant angle, enables 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 stand proud.
2. Extra time required to fill holes
3. Combination of problems
4. Some natural stones are not a constant thickness
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 a greater thickness than normal.
Using the correct material
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.
Stage 1: Use a levelling compound
A levelling compound can be used to smooth out irregularities, holes and gaps between existing tiles etc. and provide a flat and level surface for tiling. Ensure that the surface is clean, dry and sound. Any existing tiles, paint etc. must be firmly adhered.
Prime the substrate with weber PR360 and allow to dry. Pour weberfloor flex levelling compound to the required thickness. Make sure that any movement joints in the substrate are carried through the screed and tiling layer.
Fix the tiles into a solid bed of weberset plus or weberset rapid plus. Allow the adhesive to set fully and then grout the joints with weberjoint wide.
Stage 2: Use a thick bed adhesive
If the tiles/stones are uncalibrated, a thick bed adhesive must be used. This will also allow for some irregularities in the substrate.
Ensure that any loose or unsound material is removed and fix the tiles with weberset thick bed which can be built up to 25mm thick. Allow the adhesive to set fully and then grout the joints with weberjoint wide.
Stage 3: Use a patch repair mortar
For occasional deep holes in an otherwise flat surface, a repair mortar may be the best option. Ensure that any loose or unsound material is removed and that the edges are cut square, not feathered. Fill the hole with webercem pyrapatch and allow to cure.
Fix the tiles into a solid bed of weberset plus or weberset rapid plus. Allow adhesive to set fully and then grout the joints with weberjoint wide.
Stage 4: Fixing the tiles
Fix the tiles into a solid bed of weberset SPF or weberset rapid SPF. If the uncoupling membrane has cavities, fill these first with the flat edge of a trowel before spreading adhesive onto the membrane with a notched trowel. Grout the tiles with weberjoint wide flex or weberjoint pro and use weber. joint silicone sealant to fill perimeter movement joints.
Solution with the following Weber products
Styrene acrylate dispersion for use with tile adhesives, levelling compounds and webersys protect
High-performance, fibre-modified, self-smoothing, self-levelling renovation screed (up to 50 mm)
A standard-setting non-slip tile adhesive for low-porosity tiles and substrates
A rapid-setting tile adhesive for low-porosity tiles and substrates
A flexible, thick bed tile adhesive for interior and exterior use
A wide joint, mould-resistant tile grout for interior and exterior use