- Application Guide: Wall
- Application Guide: Floors
- Preparation
Walls Application Guide
Cement/Sand Render
The best substrate for wall tiling, especially in more demanding situations – strong and water resistant. It should be brought to a wood-float finish and needs to be fully cured and hard before tiling.
Plaster
Plaster is the commonest substrate for wall tiling – especially in domestic situations. It must be allowed to become fully dry before tiling and should never be used in situations where it may become wet for any length of time. It should be given a wood float finish and not be excessively polished or over tempered. Some plasters have been found not to provide good substrates for tiling.
Block and Brickwork
May be tiled directly if fair-faced otherwise should be rendered or plastered.Wall of aerated concrete block must have been allowed 6 weeks to dry before rendering, plastering, or tiling – if tiling directly, lightly dampen the surface to control suction.
Existing Tiles
Check each tile for adhesion to the substrate and refix/make good any that are suspect. Before tiling, they must be clean and free of anything, which may interfere with the bond. A ready-mixed adhesive will dry and harden relatively slowly on a tiled wall.
Floors Application Guide
Cement/Sand Screed
Screeds are the commonest substrate for floor tiling. They should be cured and dry before tiling takes place. They should have a wood-float finish and be free of anything, which may interfere with the achievement of a strong bond. Screeds, which have been laid some time before tiling, are likely to have collected dropped plaster, paint splashes, and so on – these should be removed.
Concrete
Concrete slabs which have a layer of laitance, or which has been power finished to the extent that a surface skin has been formed, should be treated to expose the aggregate. The use of Sontex pourable thick Bed can allow unevenness in the concrete to be overcome. Concreteslabs are often screeded before tiling.
Chipboard/Plywood/Tongue & Groove Floorboards
The boards must be adequately supported and firmly fixed with screws, to the joists. Board manufacturers publish recommendations for fixing. Underfloor heating ventilation must be adequate if rot is to be prevented. Fix tiles with Sontex RS2 and neWSontexWoodflex. A separation membrane could also be considered.
Existing Tiles
Check each tile for adhesion to the substrate and refix/make good any that are suspect. Before tiling, they must be clean and free of anything, which may interfere with the bond. For substrates such as asphalt, magnesite, anhydrite (calcium sulphate), terrazzo or where vinyl flooring has been lifted etc., please seek advice.
Preparation
Electric Underfloor Heating
An alternative system to the traditional method of heated water pipes laid into a screed is a thin matting system (just a few millimetres thick) which incorporates an electric heating element. This cost-effective system is thin enough to be used under ceramic floor tiles.
The substrate must be rigid in order to provide a solid background, such as a concrete or cement-based screed. Follow advice on drying times and priming instructions. An insulating tile backer board should be used to ensure maximum heat output into the room is achieved.
If tiling onto wooden floors, improve its stability by overlaying with a suitable material such as an insulating tile backer board.
Heated Screeds
Cover the newly laid screed with a waterproof sheet for seven days to prevent the screed drying out too rapidly. This stops shrinkage stress, and allows the screed to develop structural strength.
Then uncover the screed and allow it to air dry for a further three weeks (or longer depending on the ambient conditions). For further information on drying times, please refer to BS 8204. As a general rule, if a screed is a thickness of more than 50mm, then it should be applied in layers up 50mm thick to ensure a compact substrate.
Before tiling, turn off any heating for a period of 24 hours and allow to cool down.
After the tiling and grouting is complete, allow 24 hours before turning the heating back on at increments of no more than 5°C every 24-hour period to avoid cracking of the screed. Do not use the heat to accelerate the drying process of the screed.
Adhesive Application Andmethod
For underfloor heating use a polymer modified adhesive such as SontexWta Flex, applied with a notched trowel. Ensure a minimum adhesive bed thickness of 3mm with no voids between the substrate and the tile. Ensure that there is a perimeter expansion joint of 10mm in width.
Grouting
To allow limited movement when the heating is turned on, use a flexible grout. Such as SontexMulti purpose grout or Sontex Rapid Set grout.