Fixing Natural Stone tiles

Preparation

Preparation Introduction

It is of great importance that the sub floor is adequately prepared for the tiling process. This involves ensuring that the floor is level, clean and dry. Throughout the preparation process the tiles should be stored in a clean and dry area.

Types of Sub floor

The most suitable sub-floor for tiling is either a concrete, sand and cement screed or a sand and cement render. However, tiles may be laid on other surfaces such as timber floors. If the original floor is old tiles, vinyl, cork, linoleum, or woodblock, then it is necessary to remove this before laying the tiles, making sure the ground is clean, level and any old adhesive removed.

Any irregularities in the floor may be evened out by the application of adhesive during the fixing process. Where larger holes and bumps exist, a leveling compound should be used.

Concrete Floors & Sand & Cement Screeds

Please Note that a new concrete screed should be left for a period of at least four weeks before the tiles are laid. A new sand and cement screed or sand and cement render should be left for a period of two weeks. Depending on weather and site conditions, further time may be necessary.

Timber Floors

Timber floors may also be used as long as they are strong and stable enough to withstand the additional load. Timber floors can be strengthened by laying 18mm thick plywood or WBP ply wood over the entire area to be tiled and screwed down at 15 cm intervals. A flexible adhesive and a flexible grout should be used.

Under Floor Heated floors

Natural stones are very good at storing and dispersing heat and hence work very well with under floor heating. It is important to ensure that this is turned off when the tiles are being laid and that a flexible adhesive and a flexible grout are used.

Finished Floor Level

It is important to remember that the finished floor level will be raised by the thickness of the tile plus approximately 4mm for the adhesive. Thus some doors may need trimming and timber threshold strips may be required to solve of problem of varying levels of adjoining rooms.

Types of walls

The most suitable walls are solid concrete rendered walls; the weight of stone tiles needs to be taken into consideration, the average weight of most stone tiles is 25 – 30 kg/m2. In wet areas it is advisable to use tile backer boards, they are lightweight, waterproof and can support the weight of stone tiles. Walls can be strengthened by laying 15mm thick plywood or WBP plywood over the entire surface. A flexible adhesive and a flexible grout should always be used.

Layout

Introduction

Before commencing the work it is important to consider the shape of the room to be tiled and hence the layout of the tiles themselves. The tiles can be laid either in a traditional straight fashion or, if desired, brick fashioned (half bonded) at an angle in a diamond pattern resulting perhaps in a more aesthetically pleasing finish to the floor. To enhance the character of the room further, either a border or a profile may be added.

Floor Tiling Process

To begin, find the centre of the room and create a centre line from one end of the room (the end at which the door is located) to the other (the end opposite to the door) using a chalk line. Once the midpoint of this centre line is ascertained, the tiles should be laid without being fixed, so as to be able to see where the last whole tile ends. This should be done in both directions, if the gap at the end is less than half a tile, move the tiles away from the centre line until you achieve the correct gap, then mark the floor where the first tile will start.

When the actual tiling process commences, it is good practice to start at the point furthest from the door, the principal being that one does not need to step on the newly laid tiles. It is important to remember to leave a sufficient gap for the grout joint. (See Cutting and Fixing the Tiles)

Wall Tiling Process

Similar to floor tiling a start point must be ascertained, if the floor is level and you are following the line of the tiles on the walls. Use a spirit level and mark a vertical line on the wall with a pencil from the edge of the centre positioned floor tile. Then measure up the wall and draw a vertical line around the room at the correct height for an equal distribution of wall tile between the floor and the ceiling. Remember to take into account any windowsills, and the height of the bath to ensure you do not leave too many small cuts.

Cutting and Fixing

Before Tiling

VERY IMPORTANT: Before tiling it is important to ensure all the tiles are COMPLETELY DRY and free from dust both on the face of the tile and the one to be adhered. Mix the tiles to ensure that any colour, shade or batch differences are mixed to ensure a random and even distribution of any irregularities in the tiles colour and tone. These two processes are important to prevent the blocking of colours forming from the natural variation in the tile when laying them. Wet tiles should be allowed to dry because colour variation between tiles is less visible and the adhesives will not adhere correctly to wet or damp tiles.

Cutting

It is most likely that it will be necessary to cut tiles during the fixing process. Any broken or damaged tiles should be put aside and used for this purpose. Where there is a large amount of cutting to be done, a water-cooled diamond cutter should be used which will make the job much easier, and leave a very clean cut. Tiles can also be cut using an angle grinder; this may leave a rough edge but is ideal if curved cuts are needed. Both of these may be purchased from ourselves or can be rented from a hire shop.

Fixing

Although a subjective decision, it is suggested that a grout joint of approximately 2-3mm is allowed when laying stone, a wider joint may be used if required depending on the type of stone.

When tiling on a screed the tiles should then be fixed to the floor using Flexible white adhesive to ensure the surface of the tile does not become stained. The use of a sand and cement should be avoided as the tiles will take considerably longer to dry out and this may encourage efflorescence. Where the tiles are being laid on to a wooden floor, or where under floor heating is being used, it will be necessary to use Flexible white adhesive. Where the tiles are being laid outside or need to set quickly, it is important to use Rapid Flexible adhesive.

The adhesive should be spread over a small area (e.g. one square metre) of the floor to a depth of between 6 – 10mm thickness, using a square notched adhesive trowel. The direction of the adhesive should always be the same to allow air to be dispersed when the tile is bedded. . It is also advisable to butter the back of the tile to ensure a good key. Mosaics require a smaller bed of adhesive approx 3 – 6 mm thick.

The tile should then be firmly bedded into the adhesive on the subfloor, using a small twisting-like motion to ensure that there are no air pockets under the tile. This process should be repeated, remembering to leave a gap for the grout joints. It is important to ensure that the tiles are laid evenly which can be done using a spirit level. Any adhesive that is accidentally placed on the surface of the tile should be removed using a grout sponge.

Sealing and Grouting

Introduction

VERY IMPORTANT: As the tiles are natural, it will be necessary to apply a Primary Seal before the floor is grouted. A Secondary Seal may then be applied after the grouting process is completed. It is very important that the floor is clean, dry and completely free from grout stain or grease before the secondary coat is applied.

For best results the temperature in the room should not be too low, humidity in the air not too high and strong sunlight should be avoided.

Please Note. In some instances the fumes from certain sealants may be unpleasant and cause breathing difficulties for the young and old. It is important to ensure that there is good air-circulation and that an appropriate respirator is worn.

Grouting

The grouting process should commence approximately 12 to 24 hours after the tiles have been treated with a Primary Seal . This will reduce the porosity of the tiles and discourage staining..

Prior to grouting, the joints should be filled by either using a pointing process or by making up a slurry grout mixture and working the grout into the joints using a squeegee. In the case of unfilled or tumbled travertine, a slurry grout is recommended so as to fill in any holes in the surface of the tile.

Please note that only a small area (e.g. one or two square metre) should be grouted at a time before any surplus grout is removed and the grouted area cleaned using a wet grout sponge. Care should be taken not to spread the grout unnecessarily over the tiles, as it may be difficult to remove the residue when dried.

On completion of the grouting, the floor should be wiped over again to ensure that all grout residues has been removed. Once the grout has dried, the floor should be brushed to remove any dust particles.

Sealing Natural Stone

Matt Finish

Sealers used should not change the colour of the material, a product such as Lithofin Colour Intensifier should be used where one wishes to intensify the colour of the stone. Depending upon the material being treated, it may be necessary to apply more than two coats of the sealer to the floor to achieve saturation.

Primary Seal

The primary seal should be applied as evenly as possible before the floor is grouted. It is important to ensure that the tiles are completely dry, clean and stain free. The coat should be applied using a brush, roller or cloth. It is most important that all the sealer is absorbed into the tile. Any excess sealant should be wiped off before it is allowed to dry on the surface.

Secondary Seal

The secondary seal should be applied in the same way as the primary seal, but at right angles. Again, it is most important that all the Sealer is absorbed into the tile. Any excess sealant should be wiped off before it is allowed to dry on the surface. Th

Polished Finish

Ensure surface is clean, dry and free from contamination. If necessary, first clean surfaces and allow to fully dry. Apply thinly and uniformly using a soft cloth or sponge. Within 20 minutes, whilst the sealer is still wet on the surface, buff well using a clean dry cloth or buffing machine. Leave to dry for 4 hours and then on more porous surfaces apply a second coat using the same method. It is important to remember to remove any excess from the surface and buff well between each coat. Do not apply in temperatures exceeding 25°C. Ensure under-floor heating is switched off. Over applied and un-buffed sealer will dry and leave a greasy residue on the surface. To remove, apply a little more sealer and then buff immediately. If you are unsure of correct application methods, test on an inconspicuous area, prior to general application. Treated areas should be dry enough to walk on after about 4 hours .