Adhesive & Grout
When tiling walls and floors the tiles have to have firmly affixed,
using an adhesive, before being grouted. The word adhesive is an
all-inclusive term, which includes any substance that can hold materials
together, such as cement, glue and paste. Various types of adhesive can
be used in tiling; the one you choose will depend largely on where you
are tiling and the size of the tiles. Grouting is carried out after the
tiles have been affixed to the wall or floor. Grout is a cement or
chemical setting mix, which is used for filling the joints between the
There are many different types of adhesive and grouts on the market. The important message is to always read the manufacturer’s instructions; if in any doubt, ask an expert at the shop or store where you bought the tiles.
As there are a variety of
sizes and types of tiles adhered to many different types of substrates,
in all manner of locations and different conditions, there are different
types of floor and wall tile adhesive required for specific
applications. When selecting the correct tile adhesive type 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? On walls or floors? Are other
variables such as under floor heating involved?
1. Dispersion Adhesives Dispersion, or ready mixed adhesives, are supplied in tubs in a paste form. All dispersion adhesives cure 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 in more or less permanently dry conditions.
2. 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.
Applying adhesive when tiling a wall
the adhesive directly onto the wall using a special adhesive trowel.
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 metre at a time with adhesive, so you can affix 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 Multi-tool from Suretile.
10 kg of adhesive should cover four to five square metres of wall.
Grouting wall tiles
Wait at least 12 hours before grouting, unless a quick drying adhesive has been used.
The grout should be pushed firmly into the joints with a grouting sponge.
Surplus grout can be removed from the tiles using an ordinary sponge. They can then be polished with a dry cloth.
Applying adhesive when tiling a floor
type of adhesive used will depend on the type of floor. For example, a
category C2 adhesive should be used to affix 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 metres of floor. However, if the floor is not level and adhesive has to be used to level it then more will be required.
Grouting floor tiles
To allow the tiles
to bond correctly the tiles should be left to set for 24 hours, unless a
quick setting adhesive has been used.
When grouting on a timber floor a water-based polymer admixture will improve flexibility.
Use a squeegee to push the grout into the joints.
Surplus grout should be removed from tile surface using a sponge.
A grout finishing tool should be used to give the grout a smooth finish and improve its apprearance.
dry-mixed adhesives, containing self-priming, are ideal for most walls. 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 metre 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.
Grout is used to fill the gaps between adjacent tiles. It prevents moisture and dirt getting in and helps keep the wall or floor looking good. As most surfaces expand and contract over time, grout can be made more flexible by using an additive. When grouting in areas where there is likely to be a high level of moisture, such as in a bathroom or shower, you should use waterproof grout or seal it. Today, most grout is water resistant. Grout can be purchased in various colours, which means you can use it to match the colour of your tiles; there are even grouts that glitter. There are various factors that will determine the amount of grout you need for a given area of tiling. They include the size of the tiles being used and the spacing between them.
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 appear to be 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 a separate adhesive and grout which are suitable for your particular tiling project.
Q. Can I use a standard CTA on floors incorporating under floor heating?
A. No, a flexible cement based adhesive must be used. The added polymer content accommodates the movement caused by the thermal expansion and contraction created by the heating.
Q. Can I use a ready mixed tile adhesive to fix large format tiles?
A. No, it is generally accepted that a cement based adhesive should be used to fix tiles larger than 900cm2 (i.e. 300mm x 300mm). Ready mixed adhesives depend upon evaporation in order to cure. Larger tiles do not allow the water to escape from the adhesive behind them, especially on non porous backgrounds,this extends the drying times considerably.
Q. Can I tile directly onto existing tiles?
A. Yes, providing the tiles are sound, securely fixed, dry, clean and able to support the weight of the tiles and adhesive to be fixed to them. A key can be provided on glazed tiles by rubbing with course sandpaper and cleaned. Any loose tiles or tiles that sound hollow when tapped should be secured first. Consideration regarding the size and porosity of the tile should be made when choosing the type of adhesive.
Q. How do I fix natural stone tiles to floors?
A. A cement based adhesive should be used to fix natural stone, granite, limestone, marble, travertine and similar tiles. Consideration should be made as to whether a white cement based adhesive should be used when fixing lighter coloured tiles to avoid staining. ‘Solid Bed’ fixing is recommended, this is where a ribbed bed of adhesive is applied to the floor with a notched trowel and the back of the tile is ‘buttered’ with adhesive. Twisting and pushing the tile into place will provide near to 100% adhesive coverage (bedding) and support to the tile. Solid Bed Fixing is especially important when using tiles that may contain natural voids that can collapse given time.
Q. What is Travertine?
A. Travertine is a type of limestone, it has been used in Italy as early as Roman times. It has a very low density, in its natural state is full of holes and voids, these are often filled with synthetic resins on the surface. Even high quality travertines can have voids and holes throughout. The ‘Solid Bed’ fixing technique as described above must be employed in order to provide sufficient support.
Q. When can I use dot and dab fixing?
A. You can’t. The practice of dot and dab fixing is not recognised. This entails applying 5 blobs of adhesive (one in each corner and one in the centre) to the tile. This does not provide enough adhesive coverage or support to the tile.
Q. Can I use PVA as a primer before tiling?
A. No. PVA is a bonding aid for plasterers and it is not water resistant. Either an acrylic type primer or SBR should be use to prime porous surfaces before the application of tile adhesive.
Q. Do plaster walls need priming before tiling?
A. Yes. When using cement based adhesive, porous backgrounds should be primed with an appropriate primer. When using a ready mixed adhesive; priming is not required unless the surface is dusty or shiny.
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