How to tile over tile
Being able to lay new tiles over existing tiles not only saves you money, but also a lot of mess and hassle. Not all tiles can be tiled over and we look at how to successfully tile over tile.
Many homeowners are put off installing new tiles due to the amount of time and mess in ripping up old tiled floors. However, there are now products on the market that allow you to tile over the top of existing tiled floors.
Bear in mind that it isn't possible to tile over natural stone tiles such as slate, slasto or sandstone, etc., as these products tend to delaminate, but it is possible to tile over existing ceramic tiles.
It is also important that existing tiles be in good condition and be firmly fixed to the substrate. Any cracked or damaged tiles will need to be removed before installing a new layer of tiles. Similarly, any hollow-sounding tiles should be removed, as these can result in cracks in the new tiles.
GOOD TO KNOW: When looking at the option to tile over the top of existing tiles, consider that the height of the floor will increase by the thickness of the new layer of tiles. This means that skirting boards will need to be removed beforehand, and that doors will need to be trimmed.
Tiles need to be scrubbed thoroughly to ensure they are absolutely clean. Any surface contaminants on the tiles will impair the bond between old and new tile. TAL Glint is a heavy-duty tile cleaner that removes grease, oil and wax deposits from glazed tiles.
Use a hammer and cold chisel, or large screwdriver, to remove any cracked, broken or hollow-sounding tiles.
TAL Rapidfix is a rapid-set patch and repair compound that is used to fill up areas where tiles have been removed, so that they are level with the surrounding tiles. Allow repairs cure according to the pack guidelines before proceeding.
To ensure a good bond between existing and new tiles, the surface must be primed with a slurry. The slurry consists of  part Tal Keycoat mixed with  parts TAL Keymix powder. TAL products are available at Builders Warehouse countrywide.
The slurry is applied over the surface of existing tiles with a block brush, and the surface must be completely covered.
Let the slurry priming coat dry - touch-dry - before applying tile adhesive to secure the new tiles.
To bed the new tiles use TAL Tile-To-Tile quick-set tile adhesive. When tiling onto suspended slabs and for external installations mix the TAL Tile-To-Tile with TAL Bond, replacing the water in the mix.
GOOD TO KNOW: Only use a quick- or rapid-setting tile adhesive, as you want the tile adhesive to set as quickly as possible. If installed tiles are walked on too early - before the adhesive has set sufficiently - you could end up with hollow-sounding or loose tiles.
There needs to be a 6mm thick bed beneath each tile.
When installing large tiles, butter the back of the tile to ensure full contact and firm bedding.
Allow plenty of time for the tile adhesive to set before grouting - a minimum of 6 hours, but preferably overnight.
For interior tiling use TAL Wall & Floor Grout for filling tile joints up to 8 mm wide. TAL Quarry Grout can be used in wider joints up to 25 mm wide. On suspended slabs and external installations, replace water in the grout mix with TAL Bond.
GOOD TO KNOW: Wipe grout off the tile face before it hardens completely. This is especially important when an additive such as TAL Bond has been used.
When tiling over existing tiles, the existing structural and movement joints must be maintained in the new tile installation. The movement joints should be at least 5mm wide and extend through the adhesive and both tile layers. Lack of movement joints in tile installations is a major cause of tile failure.