Tiling over existing tiles and painted surfaces
Common issues and queries you can face
Difficulties with non-porous surfaces
Standard cement based tile adhesives rely on a mechanical adhesion to bond onto the substrate. The wet cement engages physically with small irregularities and pores on the surface and uses this to form a strong bond.
When the surface is very smooth this grip is much weaker causing tiles to debond.
Existing ceramic tiles and paints are non-porous surfaces such as porcelain that presents a closed smooth surface where the bonding effect may be difficult.
These types of surfaces are largely impervious to water whereas standard tile adhesive won’t gain strength until most of the water dries out.
Efflorescence
Another complication from slow extended drying is when joints are grouted before the drying of the tile adhesive is complete. Water will be trapped and it subsequently permeates through the grout carrying dissolved salts from the substrate causing an efflorescence and white deposit on the surface of the grout.
Advantages of tiling over existing tiles or paints
When tiling an area that is already tiled or painted, it is often necessary to invest considerable time in stripping and then repairing the substrate.
However sometimes, is it much easier to tile over tile the existing layer. However, this requires careful consideration and extra properties from the adhesive.
Precautions
Painted surface must be checked to ensure it is firmly adhered, with no sign of flakiness. The surface must be free from dust, dirt, grease, oil or other contaminating material. The surface should be cleaned and allowed to dry.
Existing ceramic tiles must be checked to ensure that they are firmly fixed, with no signs of any loose or drummy tiles.
