Tiling techniques: back buttering and spot fixing
As tile format seemingly get larger and larger, correct substrates and background preparation becomes more important.
To a degree, small formats and mosaics can be carefully applied to cover undulating surfaces. Large format products are less forgiving consequently surfaces have to be as flat as possible.
However, in some circumstances, tile fixers will be challenged to tile over difficult surfaces like brick or structurally sound walls that are simply not flat.
Spot fixing is an old technique that has been wideley employed to overcome uneven wall surfaces.
Tilers place a substantial blob of stiff adhesive on each orner of the tile and in the centre. THe blobl are large enough to keep the back of the tile away from the uneven wall surface, after the tile has been pressed into position.
These days, some tile fixers still spot fix tiles despite the fact that AS3958-1 2007: 54.6.2c states "spot fixing where the tiles are fixed with four or five dabs of adhesive is not recommended and should be avoided at all tiles".
Spot fixing is frowned upon because it does not comply with the contact coverage requirements stated in AS3958. In essence, it is important to avoid creating voids behind the installed tiles. But sometimes spot fixing is unavoidable, for example, when narrow slithers of tile have to be fixed in spaces where a conventional trowel simply does not fit such as gaps above or beside figures like windows. Then the fixer can add adhesive to the back of the tile and press it into place, ensuring that each piece is flush with adjacent tiles.
If spot fixing is taboo, what can be done to overcome uneven wall substrates?
In an ideal world, certainly in on where larger formats have become commonplace, substrates should be prepared in accordance with standards and they should be flat, dry and smooth.
Recommend fixing techniques include thin bed fixing. This technique should ensure that the final bed of adhesive does not exceed 3mm and voids behind the tiles are kept to a minimum.
To internal applications where there are dry conditions, notched trowel techniques should be employed using the following size trowel in relation to the tile format.
Tiles are pressed firmly into the ribs of adhesive created by the notched trowel. The adhesive is generally applied horizontally on walls to prevent moisture travelling downwards via the ribs of adhesive.
Ceramic tile adhesive should be applied in accordance with the manufacturer's instructions. Particular care should be taken to avoid spreading too much adhesive to the substrate, as it may dry before tiles can be fixed and it will lose its ability to adhere correctly to the tiles.
Note in (4) it is necessary to use added adhesive "buttered" evenly onto the back of the tiles. Contact coverage has to be maximused. The additional adhesive buttered on to the back of the tiles is often essential where contact coverage of adhesive is requird to reach or exceed 80 per cent.
Different adhesives are chosen for specific backgrounds. For example, cement based adhesives are primarily used on mature cement rendered surfaces, concrete and brickwork.
Other thin bed methods employed to fix tiel are the floating method and the buttering method. it is good practice to combine traditional application of adhesive, using an appropriate notched trowel, with back buttering techniques, espeically when alrge format tiles are specified.
The back buttering process is carried out by applying adhesive to the wall with the notched side of the trowel, a thin coat of adhesive is then applied to the entire back of the tile suing the straight edge of the trowel. The tile is then pressed into position.
A range of thick bed adhesives are available to cope with uneven surfaces, and should be employed as described above, to the maximu thickness as specified by the manbufacturer.
Builders will be fully aware of the necessity of providing flat, smooth, clean surfaces which are suitable for tiling. However, if and when fixers are challenged to tile over tricky backgrounds, there is generally a method that can be used, for brick:
Techniques like spot fixing save time and use fewer materials but are not always reliable. AS 3958-1 might be out of date and in urgent need of renewal following the introduction of slim products and other materials, however in practice it is an often used method.
Credit: Tile Today Issue 94 by Anthony Stock.
However, in some circumstances, tile fixers will be challenged to tile over difficult surfaces like brick or structurally sound walls that are simply not flat.
Spot fixing is an old technique that has been wideley employed to overcome uneven wall surfaces.
Tilers place a substantial blob of stiff adhesive on each orner of the tile and in the centre. THe blobl are large enough to keep the back of the tile away from the uneven wall surface, after the tile has been pressed into position.
These days, some tile fixers still spot fix tiles despite the fact that AS3958-1 2007: 54.6.2c states "spot fixing where the tiles are fixed with four or five dabs of adhesive is not recommended and should be avoided at all tiles".
Spot fixing is frowned upon because it does not comply with the contact coverage requirements stated in AS3958. In essence, it is important to avoid creating voids behind the installed tiles. But sometimes spot fixing is unavoidable, for example, when narrow slithers of tile have to be fixed in spaces where a conventional trowel simply does not fit such as gaps above or beside figures like windows. Then the fixer can add adhesive to the back of the tile and press it into place, ensuring that each piece is flush with adjacent tiles.
If spot fixing is taboo, what can be done to overcome uneven wall substrates?
In an ideal world, certainly in on where larger formats have become commonplace, substrates should be prepared in accordance with standards and they should be flat, dry and smooth.
Recommend fixing techniques include thin bed fixing. This technique should ensure that the final bed of adhesive does not exceed 3mm and voids behind the tiles are kept to a minimum.
To internal applications where there are dry conditions, notched trowel techniques should be employed using the following size trowel in relation to the tile format.
- 200x200mm - 8mm notched trowel
- 250x250mm - 10mm notched trowel
- 300x300 - 12mm notched trowel
- 400x400mm and above -12mm notched trowel and buttering of the tile
Tiles are pressed firmly into the ribs of adhesive created by the notched trowel. The adhesive is generally applied horizontally on walls to prevent moisture travelling downwards via the ribs of adhesive.
Ceramic tile adhesive should be applied in accordance with the manufacturer's instructions. Particular care should be taken to avoid spreading too much adhesive to the substrate, as it may dry before tiles can be fixed and it will lose its ability to adhere correctly to the tiles.
Note in (4) it is necessary to use added adhesive "buttered" evenly onto the back of the tiles. Contact coverage has to be maximused. The additional adhesive buttered on to the back of the tiles is often essential where contact coverage of adhesive is requird to reach or exceed 80 per cent.
Different adhesives are chosen for specific backgrounds. For example, cement based adhesives are primarily used on mature cement rendered surfaces, concrete and brickwork.
Other thin bed methods employed to fix tiel are the floating method and the buttering method. it is good practice to combine traditional application of adhesive, using an appropriate notched trowel, with back buttering techniques, espeically when alrge format tiles are specified.
The back buttering process is carried out by applying adhesive to the wall with the notched side of the trowel, a thin coat of adhesive is then applied to the entire back of the tile suing the straight edge of the trowel. The tile is then pressed into position.
A range of thick bed adhesives are available to cope with uneven surfaces, and should be employed as described above, to the maximu thickness as specified by the manbufacturer.
Builders will be fully aware of the necessity of providing flat, smooth, clean surfaces which are suitable for tiling. However, if and when fixers are challenged to tile over tricky backgrounds, there is generally a method that can be used, for brick:
- choose the right adhesive.
- wire brush the bricks to remove any course materials
- prime the brickwork, or use an adhesive with a built in primer.
- allow enough time for extra thick adhesive to dry before grouting.
Techniques like spot fixing save time and use fewer materials but are not always reliable. AS 3958-1 might be out of date and in urgent need of renewal following the introduction of slim products and other materials, however in practice it is an often used method.
Credit: Tile Today Issue 94 by Anthony Stock.
