Stone & Porcelain Installation
A stone, porcelain or ceramic tile is only as good as the installation, so installing correctly is of the utmost importance. In this section you will find general information on fixing as it is impossible to provide a single guide to all situations.
We are able to provide all necessary, adhesive, grout, silicone, sealants, cleaners and surface preparation products for installation as well the complete range of Schlüter products.
We can also provide specifications if required.
If you require a quotation then please provide as much information as possible so that we can provide the correct ancillary products.
The information provided should be used in conjunction with a competent Stone or Porcelain installer, together with our recommended fixing and sealing products which are carried in stock.
Stone tiles are often packed into crates very tightly, are wet at the point of production and may have some residue from the various finishing processes employed. Because of this it is recommended that stone tiles are washed with a dilution of Fila Cleaner Pro and are allowed to dry completely before every stage of the installation process. They will often lighten in colour as they dry.
Dry tiles are necessary prior to installation as any unusual tonal markings can be placed in less visible areas or used in cuts. At the point of installation always ensure that stone tiles are mixed to ensure consistency in distribution of any such variation. This will mean opening all crates or pallets of materials supplied. Patterned Ceramic or Porcelain tiles will generally come as a random mix of designs and will be boxed accordingly. Other Porcelain tiles can be used to create a variety of patterns or designs with one tile type. Because of this, all tiles should be unpacked and your fixer should be made fully aware of your laying requirements prior to the job commencing.
Stone and Porcelain mosaics are supplied with either a mesh backing or in some cases, a plastic covering to the face of the mosaic. These coverings are designed to hold the mosaic pieces in place during transport and installation only, over-handling may lead to the chips loosening or becoming dislodged completely.
Minor damage such as edge chipping is often caused in packing or unpacking tiles, and should be expected, it is deemed normal practice for these to be used as cuts during the installation process.
Tiling should start from the centre of the room and tiles should first be dry laid in order to avoid any unsightly cuts and to ascertain the optimum grout gap for your product, especially if mixing sizes or designs of tiles.
Uncalibrated stone tiles need to be graded prior to installation; the thicker tiles will dictate the floor level and should be installed first with thinner tiles being bedded up with an appropriate large format floor adhesive.
Dimensions listed are nominal as slight variations in size and thickness can occur with most Stone, Terracotta, Ceramic & Porcelain tiles as well as Stone Bathware.
All backgrounds to be tiled should be flat, level, clean, dry, and free of dust, grease and any loose material and be as free of movement as possible.
Make sure that you have discussed your requirements fully with your stone fixer and that they are familiar with the product to be fixed and your expectations.
Lighting on site during fixing should be as similar as possible to that which will be present in the final installation.
All Stone, Terracotta, Ceramic & Porcelain tiles must be solidly bedded, with 100% adhesive coverage; cement-based tile adhesives are the most appropriate for this method. It may be necessary to ‘butter’ the back of some tiles if they are large-format, travertine or have deep texture to the back of the tile, to ensure full adhesive coverage.
During the fixing process, occasionally a tile should be lifted to check that full coverage and compaction is being achieved.
We offer rapid or standard setting adhesives in either white or grey. Click here to view our full range of Ardex Tile Adhesives.
Fast setting adhesives allow moisture to disperse more quickly so are best for use with large-format natural stone, terracotta and porcelain. This helps to prevent various reactions that could be caused by the moisture retention of the tile.
Standard setting adhesive has a longer working time, which allows more time to make the minor adjustments and tweaks which are necessary when fixing smaller stone, porcelain or ceramic tiles.
Some tiles require the use of specific adhesives to ensure problem free fixing; please speak to one of our branches in order to obtain the best advice for your specific installation.
If fixing a light coloured tile, or using a light coloured grout, use a white adhesive to avoid any shadowing through.
All of our adhesives are flexible adhesives so suitable for the vast majority of substrates, if there is any degree of movement within the substrate then additional surface preparation should be undertaken.
Grout & Silicone
Grout joints are in place to allow for any movement of tiles and should be a minimum of 3mm or more, depending on the size and finish of the tile.
Stone tiles with a textured surface tend to have grout joints of 6-10mm, whereas smoother Honed and Polished stones as well as Porcelain tiles can be jointed at about 3-5mm.
The width of joint selected should be sufficient to accommodate any variation in tile sizes.
When fixing a mix of sizes such as an opus pattern, the grout gap will vary in width due to the layout of the tiles in the pattern.
Ardex FL Flex Wall & Floor Grout is available in 10 colours to best suit your choice of tile. The choice of grout colour will also have a bearing on the colour of adhesive required as a grey adhesive may shadow through a light coloured grout.
Grouting should not take place for at least 12 hours after the tiles have been fixed. Grout joints should be completely clear of any building dust or residue.
‘Slurry’ grouting with the appropriate colour of grout is necessary with unfilled Travertine, some Limestone and occasionally with other tile types, in order to fill naturally occurring pits and crevices. Most other stones types and finishes including Honed, Polished, Brushed & Riven materials, as well as Porcelain, should however be pointed in order to avoid grout residue being left on the surface of the tile.
Any grout residue on the surface of the tiles should be wiped off as part of the grouting process and it is recommended to perform an intermediate wash with dilute Fila Cleaner Pro after grouting but before additional sealing. Any grout residue left on the surface may prove difficult to remove if left too long.
Ardex ST silicone should be used to seal joints around shower trays & baths, at junctions of walls, and walls & floors, and is available in a range of colours to complement our range of grouts.
All stone and Terracotta tiles should have an initial sealant coat after fixing but prior to grouting as some tiles may absorb pigments from the cementitious grout.
Heavily pigmented grouts may be subject to efflorescence as the salts which hold in the pigmentation are released as part of the drying process
Stone, Porcelain & Ceramic tiles all have varying densities and properties and will behave differently when being cut. It is important to use the best equipment possible in order to achieve the best possible result.
Cutting should be carried out using a water-cooled, bench power saw with a diamond blade. It must however be noted that the final aesthetic finish achieved will depend greatly upon the choice of cutting mechanism and level of skill of the operator. Equipment and blades specifically for the cutting of the particular product being fitted should be used.
Where necessary, the cutting blade should be water suppressed whenever cutting to control dust and cool the blade.
Please note that high quality diamond blades should be utilised at all times. If a blunt or worn diamond blade is used, shelling or chipping of the tile edge could occur.
If more than 25% of a flag or slab requires cutting then the remaining piece should be cut from the internal corner of the cut to the external corner of the flag or slab, at an angle of preferably 45°.
With some materials or intricate cuts, it may be necessary to cut ‘outside’ of the desired finished edge and then ‘dress’ the edge accordingly so as to achieve a neat, finished edge.
The above guidelines are general, for information on specific products, please contact us.
The key to preventing problems occurring after the installation of your tiles is the correct preparation of the substrate prior to fixing. All substrates that are to be tiled to, be they floor or wall, should always be suitably prepared; they should be clean, flat, level, free from movement and free from anything which could be deleterious to adhesion.
Correct identification of the substrate is vital to ensure the correct advice and ancillaries are provided. With the increasing use of large format materials on walls, it is imperative to ensure that the substrate has a suitable weight bearing capability to accommodate the desired material. For guidelines on fixing to specific substrates please click here.
Floors – Sand/Cement Screed
A dry level screed is an ideal fixing substrate. New screeds usually need to cure for a minimum of 1 week for every 25mm of screed depth, although the installation contractor should always be consulted for more specific timescales.
If time does not allow for this then Schlüter-DITRA 25 matting can be installed on a drying screed as it allows moisture in the substrate to evaporate through its air channels, thus neutralising vapour pressure and bridging any cracks that will occur through the natural drying out process. If this is done then the movement joint at the perimeter of the room must be left open.
Uneven floors can be overcome to a certain extent with Ardex K40 HB Levelling Compound which can be used to create a smooth & level surface prior to tiling.
Floors – Calcium Sulphate/Anhydrite/Gypsum Screed
These types of screed are mixed much wetter than conventional sand/cement screeds in order to be pourable and self-levelling. This means that whilst installation of the screed is much quicker, due to the much higher water-content, curing times are much longer. In addition, they are not considered suitable for damp or frequently wet areas such as wet rooms or pool areas.
These screeds must be cured thoroughly to their respective manufacturer’s recommendations before tiling can begin as they retain moisture for longer periods than conventional sand and cement screeds.
Approximate curing allowances are 1 day per mm thickness of screed up to 40mm and 2 days per mm for any additional thickness over 40mm, however, the screed manufacturers should be contacted for their recommendations.
If the installation is to be fixed with a cementitious adhesive, tiling should not commence until the screed has a residual moisture content of less than 0.50%.
Alternatively Schlüter-DITRA 25 matting can be used to neutralise the vapour pressure and lay on a screed with a moisture content of 2.0% by volume or less.
The use of Schlüter-DITRA 25 matting as an uncoupling membrane will be beneficial in minimising the risks of cracking.
The surface of the screed should be sanded down to remove any fine laitance which may be left and the screed then vacuumed ready to be primed.
Smooth and non-porous calcium sulphate screeds should be sealed with a coat of 1 part Ardex P51 Primer to 0.5 part water.
Absorbent and smooth or pumped calcium sulphate screeds should be sealed with a coat of 1 part Ardex P51 Primer to 3 parts water.
Floors – Underfloor Heated Screed
This is usually a water piped system and should be a system suitable for use with stone, porcelain or ceramic flooring. The system should be installed in a minimum screed depth of 65mm, incorporating the pipes, in accordance with British Standards.
After the screed has ‘cured’ the heating should be brought up to operating temperature at a rate of 5°C per day. The operating temperature should then be maintained for 2-3 days before being allowed to cool down to room temperature. Whilst installation takes place, the temperature should be maintained at 15°C (unless it is an Anhydrite, Hemihydrite or Gypsum Screed).
If the screed cannot be heated prior to tiling or the screed has developed stress cracks, Schlüter-DITRA 25 matting should be used over the whole floor area to bridge potential or existing screed cracks to eliminate transference to the tiled floor covering.
After fixing tiles, leave heating switched off for at least 14 days before bringing the floor to a gradual operating temperature at a maximum rate of 5°C per day, up to a maximum temperature of 40°C, although your underfloor heating supplier will be able to offer more specific advice.
Floors – Undertile Heating
Usually an electric mat or cable system, the undertile heating system used should be suitable for use with natural stone, porcelain or ceramic flooring. Bed the heating mat into a layer of Ardex K40 HB Levelling Compound which will protect the heating elements from any damage during the fixing process.
Schlüter-DITRA 25 matting should be installed on top of the cured Ardex K40 HB Levelling Compound to isolate the tile covering from the heated substrate underneath. This prevents movement stresses from damaging the tiled surface. Schlüter-DITRA 25 matting will not inhibit heat transfer or reduce the efficiency of the heating system.
Floors – Existing Tiles
Any loose tiles should be removed and the floor degreased and thoroughly cleaned prior to fixing.
Vinyl tiles will require sealing prior to fixing with suitable adhesives.
Unglazed tiles or natural stone that have been thoroughly cleaned can be adhered to with any suitable adhesive without remedial action.
Floors – Movement Joints
Movement joints are used to allow surfaces to expand and contract or to mimic any movement which is already present.
Structural movement joints in the flooring and bed must be sited directly over and be continuous with any structural joints in the base structure.
Perimeter movement joints are necessary where the flooring abuts restraining surfaces, such as perimeter walls, columns, kerbs, steps etc. These joints should always be installed unless the distance between walls is less than 2 metres.
Intermediate movement joint requirements depend on the dimensions of the floor. In floors with less than 10 metres between perimeter joints, generally no intermediate movement joints are necessary; however, they are required to divide larger areas, and these are normally placed at not more than 10 metres apart. Ideally, the distance between all joints (intermediate and perimeter) should be equal, unless other features of the installation dictate otherwise.
If underfloor heating is incorporated, areas without intermediate movement joints should not exceed 40m² if using an uncoupling membrane such as Schlüter-DITRA (recommended), with a maximum 8 metres between joints. If no uncoupling membrane is used then this area should be decreased to 25m².
On suspended floors the bay size should be reduced and additional movement joints should be placed directly over supporting walls or beams.
Schlüter-Systems are able to offer bespoke specifications for movement profiles. Please find their contact details at the end of this technical section.
Floors – Problematic Substrates
Used for multiple purposes, Schlüter-DITRA 25 matting is a membrane with a 3mm thick grid structure and is designed to act as an uncoupling layer for problematic substrates. Differing floor substrates can be overlaid with this matting to eliminate stress cracks from lateral movement at their abutments, it may be necessary to use a movement profile to alleviate any vertical movement; it can also be used to bridge screed cracks
All types of wood or boarded floors are particularly affected by moisture and flex. These floors should be overlaid with a suitable construction board, screw fixed at 300mm centres across the board and 150mm centres along the edges to minimise movement. Schlüter-DITRA 25 matting serves as a waterproof membrane and as a vapour pressure equalisation layer for floors to accommodate moisture occurring at the underside. It also uncouples the floor covering from the substrate and prevents the transfer of lateral stresses to the tiled surface.
If using Schlüter-DITRA 25 matting then the minimum tile size that can be used is 50mm and the maximum adhesive bed thickness on top is 10mm.
Un-cured mortar screeds, heated screeds, floating screeds and Gypsum screeds can be subject to deformation due to residual moisture, shrinkage, load stresses or temperature changes. Using Schlüter-DITRA 25 matting and providing the substrate is sufficiently load-bearing, the tile covering can be installed immediately.
For any queries, please contact us.
Floors – Exterior Substrates
Ground preparation for Stone Flagstones or Cobbles depends upon the intended use of the paved area and the site conditions.
Care must be taken to pave or cobble at least 150mm below the damp-proof course of a building and a gradient of 1:60 is necessary to provide a ‘fall’ to drain water away from a building.
A stabilising layer of at least 100mm of scalping/crushed hardcore must be installed, thereafter a 30-40mm sand bed should be compressed with a vibrating plate compactor. The perimeter tiles should then be bedded in a wet mortar in order to ‘anchor’ the tiles and prevent ‘spread’. The remaining tiles can then be solidly bedded into a semi-dry or dry 4:1 sand/cement mix, dependent on stone thickness.
Consideration should always be given to the porosity and shade of any stone, for example, a very pale stone should not be laid with a wet mix as pigments from the cement may bleed into the stone.
The correctly prepared substrate will support all exterior stone tiles, immaterial of their thickness.
Once fixed, the grout gaps can be filled either with sharp or pit sand which can be brushed into dry joints.
The above information is for stone tiles of 20mm or over (please check suitability of material) & 20mm exterior porcelain tiles. Thinner tiles, including a majority of our Porcelain range, can be laid externally although they will have to be laid on a concrete slab with adhesive & grout, as per internal applications. The concrete slab should be designed & installed to the relevant standards. Please feel free to contact us to check suitability of materials for use externally.
Walls – Sand & Cement Render
This is a good vertical base for fixing stone tiles up to a thickness of 15mm (≤38kg/m² approx) with a maximum fixing height of 3.6 metres with suitable Wall Tile Adhesive. To accommodate up to 20mm thick tiles (≤50kg/m² approx) the render must be reinforced with stainless steel EML or similar. New renders need a minimum of two weeks to dry out.
Walls – Plasterboard
Plasterboard that has not been skim coated with a finish coat of plaster will take most 10 and 12mm thick tiles (≤32kg/m² approx). In these cases the paper face of the board should be sealed with a coat of Ardex P51 Primer mixed 1:4 parts water and allowed to dry, the tiles can then be fixed with Ardex X7 or Ardex X7 R Wall & Floor Adhesive.
Plasterboard is not a suitable substrate for use in wet areas, wet rooms or other areas subject to consistent wetting.
Walls – Backerboard/Construction Board
There are various construction boards/tile backer boards available, generally they are cementitious, glass-fibre reinforced or extruded polystyrene, and are either water resistant or waterproof. They are available in various thicknesses which will all have varying weight bearing capabilities. When suitably screw fixed to walls they should provide an approximate load bearing facility of 40- 50kgs/m² which is generally an adequate load bearing substrate for stone tiles up to 15mm in thickness. Some backerboards are able to accommodate 60-70kgs/m² which is ideal for fixing thicker Splitface materials although the cladding or panels may need to be supported until the adhesive dries. Individual manufacturers should always be contacted for the relevant information on load-bearing capabilities.
Walls – Plaster Skim
If it hasn’t already been done, then plastering walls should be avoided as it adds costs, increases installation times and significantly limits the tiles that can be applied to the wall.
Gypsum plaster should have been cured for at least 4 weeks prior to installation. Having a very low weight bearing capability of up to 20kgs/m², only very light and thin porcelain or ceramic tiles can be fitted to gypsum plaster, natural stone and most porcelain tiles are generally too heavy.
Always check that your chosen tiles are suitable prior to ordering.
Suitable tiles can be fixed with any suitable cementitious adhesive, once the skim has dried to a RH of 85% or less. The skim should be primed with one coat of Ardex P51 Primer diluted 1:3 with clean water prior to fixing.
Walls – Movements Joints
All existing movement joints in the substrate must be carried through to the finished surface with a surface movement joint positioned directly over background or plane changes within the substrate.
Intermediate movement joints should be placed vertically at 4 metre centres and at internal corners and columns,
Horizontal movement joints should be positioned at junctions with floors and ceilings.
Movement joints at junctions can be sealed with a suitable silicone or alternatively, a wide range of movement and control joint profiles, as well as advice on usage are available from Schlüter Systems.
Walls – Problematic Substrates
Some plaster skim, existing tiles and painted walls are not deemed suitable substrates as they do not have the weight bearing capacity required to take most stone and porcelain tiles.
If the underlying substrate is capable of supporting the installed load then a proprietary tile backer board (such as Schlüter-KERDI-BOARD, which is waterproof and insulating), should be suitably primed where necessary, then screw fixed firmly through to the substrate in order to create a surface to which the tiles can be affixed.
Wet Areas, Tanking & Floor Drains
When planning a wet room the background must be stable and rendered watertight against moisture before tiling begins.
Always give consideration to the best material to use. Natural stone is beautiful and unique but is also porous to varying degrees and may contain minerals that can react with water over time. Porcelain tiles are non-porous and have high-grip finishes.
Tiles themselves don’t form a waterproof layer, therefore wetrooms and any other areas which will be subject to high levels of water should have the substrate underneath water proofed or ‘tanked’. This process prevents any damage to the underlying surfaces. Suitable tanking can be achieved by use of Schlüter waterproofing membranes, sealant adhesives and drainage systems.
Water resistant adhesives, grouts and substrate materials should always be used, even when tanking. Use of substrate materials which are susceptible to damage by prolonged exposure to moisture should be avoided.
Any fall required in a wet room should be incorporated in the substrate where possible, Schlüter have a range of preformed showerbases, for use in conjunction with their range of floor drains, to help with this.
Schlüter-KERDI matting is a waterproof membrane made of soft polyethylene, which has been covered in a special fleece to anchor the membrane to the tile adhesive. This membrane can be fixed to any even, load bearing, nonflexible substrate with a thin bed of adhesive. In order to maintain a watertight seal the edges should be over-lapped by 50mm. These joints must be sealed with an application of Schlüter-KERDI-COLL adhesive sealant to form a complete watertight seal.
Schlüter-DITRA 25 matting is a waterproof polyethylene membrane with a grid cavity structure and an anchoring fleece on its underside for use on floor substrates. It can be adhered to the underlying substrate using a thin bed of adhesive. If a waterproof seal is required, the joints should be overlaid with Schlüter-KERDI-KEBA tape, and sealed with Schlüter-KERDI-COLL adhesive sealant.
When using Schlüter-DITRA 25 matting the tile dimensions should be a minimum of 50x50mm, and the adhesive bed a maximum of 10mm thick.
Schlüter-DITRA 25 matting serves a dual purpose for boarded substrates, firstly as a waterproofing membrane, when the mat joints have been sealed with Schlüter-KERDI-KEBA tape and Schlüter-KERDI-COLL adhesive sealant; secondly as an uncoupling or separating membrane between the floor and the tiled surface above to prevent stress cracks from transference of lateral movement.
Schlüter offer a range of floor drains which when combined with Schlüter waterproofing materials can provide a complete wet room solution. Floor drains are stocked with either 150x150mm or 100x100mm square stainless steel grates or alternatively as linear grill ranging from 500-1800mm in length.
It is important when choosing a shower to compare the output of the shower, with the drainage capacity of the drain. We can obtain other linear grill sizes and designs from Schlüter’s range as well as levelling boards and preformed showerbases.
Showers should not be used for 14 days after grouting.
Hot Weather Working
A majority of tile adhesives, grouts & levelling compounds, including Ardex products are designed to work at 20°C. At higher temperatures, precautions are needed as the mortars will stiffen and harden more rapidly, reducing the available working time. In addition, the accelerated drying factor caused by hot weather and warm dry winds can increase the risk of shrinkage cracking.
- Storage of Products: Always ensure that Ardex products are stored away from direct sunlight. Products stored outside need to be shaded and protected from the elements. High temperatures can also drastically heat up materials stored in vans and other vehicles. The same rules apply to associated materials such as aggregates for screeds.
- Mixing water: Always run the mix water until it is cool before using it to mix an Ardex product. Beware that hosepipes exposed to direct sunlight can heat water up rapidly, so they should be shaded. Water stored in buckets, water drums and other on-site methods should be avoided where possible, otherwise be shaded and protected from direct sunlight.
- Mixing Area and Tools: Mix Ardex products in a shaded area to avoid the mixing tools becoming hot – ensure that tools are quickly cleaned after use to avoid build-up of material and contamination between mixes.
- Substrate Temperature: Is very important as warm surfaces will accelerate setting. A surface thermometer, infra-red or the Protimeter MMS/2 machines, can be used to plan installation procedures. Tenting/shading/wind breaks or working early in the morning can help control substrate temperature.
- Substrate Preparation: In some cases, absorbent substrates such as concrete, aerated block, render, brickwork etc. may have higher porosity than under normal conditions. To help with application and reduce suction, consider damping down the surface with water or priming with a 1:7 mixture of water and Ardex P51 Primer.
- Size of Working Area: Consider reducing the size of working areas at the planning stage to ensure that the materials are installed as quickly as possible.
- Accelerated Drying Protection: To reduce the increased risk of surface shrinkage, cracking, and differential drying, shade the working area and use temporary wind breaks. For screeded areas an impervious protective sheet should be considered.
Always prepare products in accordance with the relevant Ardex product datasheets.Mandarin-Stone-Ardex-Hot-Weather-Working (.pdf)
Our range of ancillary products has been extensively researched over the years to ensure their best compatibility and performance with our stones and their intended applications. All of our suppliers are regarded as leaders within their industry. Prices are checked to ensure they are competitive in the marketplace and we are happy to give you a no obligation quotation for such products alongside your stone. Where alternative products are being used, please check their compatibility with the suppliers or manufacturers before use. All stones photographed for this website, printed media and displayed in our showrooms have been finished with appropriate ancillary products recommended by ourselves. If you have any special considerations or needs for your installation then please feel free to contact us so that we can offer the correct advice and products for the situation.
All advice and instructions, while they are the results of studies and trials carried out, are provided for informative purposes only.