When selecting the correct tile adhesive for the job in hand, the following factors should be taken into account; the size and weight of the tile, porosity of the tile and substrate, type of substrate and the ambient conditions the installation will be subjected to during its life: are the conditions wet, damp, permanently immersed or dry? Are they internal or external? is it for walls or floors? Are other variables such as under floor heating involved?

MAIN TYPES

Dispersion Adhesives

Dispersion, or ready mixed adhesives are supplied in tubs in a paste form. All dispersion adhesives cure or dry/’go off’ by evaporation, no chemical reaction or chemistry takes place during curing. For this reason dispersion adhesives are not recommended for use when using large format, impervious tiles or impervious backgrounds as the water cannot escape. Dispersion adhesives have their place, when used on walls with tiles having a surface area no greater than 900cm2 and in more or less permanently dry conditions.

Cementitious Adhesives

These are supplied in powder form to be mixed with a measured amount of water. Cement based floor and wall tiling adhesives are generally superior in performance to dispersion adhesives, they can be used either in place of ready mixed adhesives or can be used where the conditions do not permit the use of a ready mixed product. Cement cures by chemical reaction (cement hydration), not just by evaporation. Care should be taken that porous backgrounds are correctly primed in order that the water is not ‘sucked’ out of the adhesive before the cement has hydrated. Because having a route for any water to escape by evaporation is not such an issue, cement adhesives can be used with large format tiles, including very impervious (non porous) tiles such as porcelain and on impervious backgrounds. Depending on the grade or classification, cement based adhesives can be used in installations with under floor heating systems where thermal movement is likely, when tiling on plywood boarded floors where limited movement or vibration is likely, or even in permanently immersed locations such as swimming pools.

Dry-Mixed Adhesives Containing Self-Priming

This type of adhesive is extremely convenient, as you do not have to mix it or prime the wall before tiling. For walls susceptible to damp, such as in a bathroom, a water resistant adhesive should be used; otherwise standard adhesive is good enough. Usually, adhesives designed for floor tiling are water resistant. If you are tiling a concrete floor it is always best to use a non-flexible adhesive, but on wooden floors and floorboards a flexible one should be used.

Normal and rapid-set adhesives are available for both wall and floor tiling. With normal adhesives you will have to wait up to 24 hours before you can commence grouting. With rapid set the wait is reduced to only a few hours.

The problem with rapid set adhesive is that it can set more quickly than you are able to lay the tiles. With the normal variety, when spread over an area of one square meter at a time, you will not have any problem with it drying before the tiles are laid. Adhesives are sold in a variety of colours, which is not a problem unless you are fixing natural stone tiles. Coloured adhesive will stain them, so be sure to only use white adhesive.

Applying Adhesive When Tiling A Wall

Spread the adhesive directly onto the wall using a special adhesive trowel with the correct notch size. There are two methods – single and double spreading. With single spreading, the adhesive is spread on either the wall or the tile. With double spreading, the adhesive is spread on both the wall and tile and gives the best level of adhesion. Cover no more than one square meter at a time with adhesive, so you can fix the tiles before it forms a skin. Press and then twist the tile onto the wall. Clear any surplus adhesive from between the joints. A useful tool for this is the Suretile Multi-tool. 10 kg of adhesive should cover four to five square meters of wall.

Applying Adhesive When Tiling A Floor

The type of adhesive used will depend on the type of floor. For example, a category C2 adhesive should be used to fix files on wooden floors. When tiling over hard vinyl tiles, the existing tiles must be primed and dried before the C2 adhesive is spread over them. When tiling on top of other tiles they must also be completely free of any dirt or grease and firmly fixed. C2 adhesive should be used when laying the new tiles. 20 kg of adhesive should cover five square meters of floor. However, if the floor is not level and adhesive has to be used to level it then more will be required. However, do not use adhesive to build up a very uneven floor but level it properly first i.e. with a self leveling compound.

Problems Using Combined Adhesives And Grouts

There are combined adhesives and grouts available on the market, but you are advised not to use them. Though purchasing combined adhesive and grout might seem like a good way to save on expense and finish the job much more quickly, many who have used these products have run into problems. Typical complaints are that the combined adhesive and grout is low quality and it is difficult to achieve an acceptable finish. Also, when the ‘grout’ is set it contains little holes and has to be replaced. The answer is to always use separate adhesive and grout which are suitable for your particular tiling project.