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Tiling over existing tiles and painted surfaces

 

 

Case

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, 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 that are closed. Porcelain presents also a closed 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 water dries out.

 

 

Efflorescence

The other complication from slow extended drying is when joints are grouted before the drying is complete. The water will be trapped, and it subsequently permeates through the grout carrying dissolved salts from the substrate causing efflores­cence 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.

It is sometimes much more straightforward to 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.

Solution

Substrate preparation

Drummy tiles should be removed and the gap should be filled with a suitable repair mortar, like Conrep.331 TX.

Methode of application

 

Tile adhesive

Mix and apply weber.col plus with the suitable notched trowel.

For large tiles, only a flexible tile adhesive like weber.col flex should be used.

Also the back-buttering method is recommended.

If the substrate is non porous (porcelain tiles, etc...), priming is highly recommended with weber.col prime

Tile grouting

It is recommended to have a minimum joint width of 2 mm around the tiles. Grouting should be done at least after 24 hours of fixing tiles, using weber.joint deco or weber.joint perfect.

 

 

Important Note

• In certain environments where high chemical resistance is needed, it is recommended to

use weber.joint epo for grouting.

 

 

Solution with the following weber products

Solution

webercol flex

Two components high performance cementitious flexible tile adhesive (latex modified)

Solution

weberjoint/ weberjoint thick

Cementitious tile grout

weberjoint perfect

High performance, Low Stain, cementitious tile grout with Hydro Repell and Mould Stop technologies