Stone & Porcelain Installation
Choosing the correct way of installation for your chosen material is as important as choosing the product itself. This part is to give only general information on fixing, since it is not possible to suggest single guide according to the variety of factors that need to be taken into consideration, to specify adhesives, grouts, sealants or other specialist ancillary materials.
If you would like to receive a particular suggestion and advice then please fill us with any necessary information that we will be able to supply the correct supplementary products. The information given is suggested to be used in company with a competent Stone or Porcelain installer, together with our suggested fixing and sealing products that are in stock.
Stone tiles are generally packed into wooden containers very tightly, are wet at the process of production and may have some silt from the numerous finishing processes applied. Henceforward, washing stone tiles with a suspension of Fila Cleaner and drying them completely before moving on to next stage of the installation process is strongly recommended. They may seem to lighten in colour as they dry.
Dry tiles are necessary prior to installation as any unusual tonal markings can be located in less visible areas or used in cuts. At the point of installation always make sure that stone tiles are mixed to establish consistency in distribution of any such variation. This means opening all boxes, crates or pallets of materials provided. In most cases Patterned Ceramic or Porcelain tiles will arrive as a random mix of designs and will be crated in accordance. Other Porcelain tiles can be used to design and construct a variety of patterns or designs with one tile type. Therefore, all tiles should be uncrated and the fixer should be fully aware of your laying requirements before the job initiate.
Stone and Porcelain mosaics are provided with either a mesh backing or in some cases like a plastic covering to protect the face of the mosaic. These coverings are formed to hold the mosaic pieces in one place, and protect them during transport and installation only, over-handling may lead to the chips loosening or becoming dislodged completely.
Minor damages such as edge chipping generally takes place during the process of packing or unpacking tiles, and it should be expected, it is deemed normal practice for these to be used as cuts during the installation process.
It is recommended that tiling should begin 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 should be graded before the installation; the thicker tiles will dictate the floor level and should be placed first with thinner tiles being bedded up with a convenient 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.
Also, 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.
Assure that you have explained and discussed your requirements completely 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 should be solidly bedded, with 100% adhesive coverage; cement or gypsum-based tile adhesives are the most applicable for this method. Some of the travertines or large format tiles may need to be ‘buttered’ with adhesive on the back to have complete adhesive coverage.
Sometimes tiles need to be lifted during the laying process to make sure that adequate compaction and full bed adhesion is being completed.
Fast setting adhesives are recommended in order that the moisture diffuses quickly from the Stone or Terracotta. This is helpful to avoid numerous reactions that could be faced because of the moisture retention of the tile.
Standard setting adhesives have a longer working time, by that, allowing more time to make minor adjustments and changes during the installation process, optimal for fixing smaller stone, porcelain or ceramic tiles.
Some of the tiles necessitate the use of particular adhesives to ensure problem free fixing; please speak to one of our branches to have the best advice for your specific installation.
Light materials generally require fixing with white adhesives to avoid any possible discoloration should the alkaline mortar bleed into, or react with the minerals within the body of the stone itself and also to avoid shadowing through to the associated light colored grout.
Flexible adhesives, mixed with further substrate preparation, are needed when the substrate is plywood, existing glazed tiles (floor application only), under floor and/or under tile heating is present or there is any degree of movement or instability in the substrate.
In addition, the appropriate Large Format Flexible Floor Adhesive, such as Norcros Thick Bed Grey Flexible Adhesive should be chosen to accommodate the discrepancy in tile thickness and associated increase in adhesive bed thickness. This will be noticeable if laying a mix of sizes in an uncalibrated material.
Grout & Silicone
Grout joints are in place to let any movement of tiles and need to be a minimum of 3mm; it is not possible to ‘butt-joint’ tiles with the exception of Splitface materials that are formed to be fitted this way. However, some grouting may be necessary according to the situation.
Stone tiles have a textured surface may have grout joints of 6-10mm, while smoother Honed and Polished stones as well as Porcelain tiles may be jointed at about 3-5mm.
The width of joint selected should be adequate to accommodate any deviation in tile sizes.
When fixing a mix of sizes such as an opus pattern, the grout gap will differ in width by cause of the layout of the tiles in the pattern.
Grouts are available in a range of colours to 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 grout.
Some materials need the use of specific grouting materials, such as Norcros 4 into 1 Grout. Please get in touch with nearest showroom for specific advice.
Grouting should not be carried out for at least 12 hours after the tiles have been fixed. Grout joints should be entirely clear of any building dust or residue.
‘Slurry’ grouting with the convenient colour of Norcros Flexible Wall & Floor Grout or Norcros 4 into 1 Grout is needed with unfilled Travertine, some Limestone and sometimes with other tile types to fill naturally occurring pits and crevices. However, most other stones types and finishes including Honed, Polished, Brushed, Flamed and Riven materials, as well as Porcelain, need to be pointed in order to prevent grout residue being left on the surface of the tile.
Any grout silt on the surface of the tiles need to be wiped off as part of the grouting process and it is advised to perform an intermediate wash with dilute Fila Cleaner after grouting but before additional sealing. Any grout debris left on the surface may get difficult to remove if it stays too long.
Norcros 4 into 1 grout contains an anti-bacterial agent to endure mould, thus it is optimal to use in bathrooms and wet areas.
Norcros 4 in 1 Silicone should be used to seal joints around shower trays & baths, at junctions of walls, and walls & floors, and is possible to find in a range of colours to complement our range of grouts.
All stone and Terracotta tiles should have an basic, initial sealant coat after fixing but prior to grouting as some tiles may take in pigments from the cementitious grout.
Heavily pigmented grouts may be subject to efflorescence as the salts that hold in the pigmentation are released as part of the drying phase.
The best way to avoid and possible problems occurring after the installation of your tiles is the right preparation of the substrate before the fixing. All substrates that will be tiled to, be they floor or wall, should always be appropriately prepared; they must be clean, flat, level, free from movement and free from anything that can be damaging for the adhesion. Accurate identification of the substrate is very important to assure the right advice and ancillaries are given. With the increasing use of large format & Splitface materials on walls, it should be ensured that the substrate has an appropriate weight bearing capacity to accommodate the requested material. For help and guidance for fixing to specific substrates please click here.
Floors - Sand/Cement Screed
A dry level screed is a very convenient fixing substrate. New screeds usually takes a minimum of 1 week to cure for every 25mm of screed depth. However, it should always be consulted to the installation contractor for more specific timescales.
If it is not a suitable option time wise, then Schlüter-DITRA 25 matting can be used on a drying screed since it allows moisture in the substrate to evaporate through its air channels, so that neutralizing vapor pressure and bridging any cracks which may appear during the process of natural drying out. After accomplishing it, the movement joint at the perimeter of the room should be left open.
Floors that are not even can be overcome to a certain extent with Norcros Pro 30 Fibre Levelling Compound or alternatively a Large Format Flexible Floor Adhesive, such as Norcros Thick Bed Grey, can be chosen to fix tiles up to a maximum bed thickness of 25mm.
Floors - Calcium Sulphate/Anhydrite/Gypsum Screed
These types of screed are mixed much wetter than conventional sand/cement screeds to have it in more pourable and self-leveling form. Thus, the installation of the screed becomes much quicker, thanks to the much higher water-content, curing times are much longer. It should also be taken into consideration that they are not considered convenient for damp or frequently wet areas such as wet rooms or pool areas.
These screeds should be fixed thoroughly to their respective manufacturer’s advice before tiling can start as they retain moisture for longer periods than conventional sand and cement screeds.
Estimated 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, it should be consulted to the screed manufacturers to get their recommendations.
Tiling should not commence until the screed has a residual moisture content of less than 0.50%, if the installation is to be fixed with a cementitious adhesive.
As an alternative Schlüter-DITRA 25 matting can be also chosen to neutralize the vapor pressure and lay on a screed with a moisture content of 2.0% by volume or less.
The application of Schlüter-DITRA 25 matting as an uncoupling membrane can be beneficial to minimize the cracking risks.
The screed’s surface needs to be sanded down to remove any fine laitance that can be left and the screed then vacuumed ready to be primed.
Later on, the screed’s surface needs to be sealed with progressively stronger coats of Norcros Prime Bond prior to fixing of tiles. The initial coat must be diluted 1:4 with water and allowed to dry; after the initial coat, the next one should be diluted 1:3 and applied to the surface at 90° to the previous coat. If the screed is still absorbent, a third coat diluted 1:2 needs to be implemented at right-angles to the previous.
Floors - Underfloor Heated Screed
This one is generally a water piped system and needs to be a system that convenient for stone, porcelain or ceramic flooring use. The system must be built in a minimum screed depth of 65mm, incorporating the pipes, according to the British Standards.
After the screed has ‘cured’ the heating should be brought up to operating temperature at a rate of 5°C per day. Then the running temperature should be maintained for 2-3 days before cooling down to room temperature. When installation takes place, the temperature must be maintained at 15°C (unless it is an Anhydrite, Hemihydrite or Gypsum Screed).
Unless the screed can be heated prior to tiling or if the screed has developed stress cracks, Schlüter-DITRA 25 matting must be used over the whole floor area to bridge potential or existing screed cracks to avoid transference to the tiled floor covering.
After fixing tiles, leave heating turned 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 can offer more specific suggestion.
Floors - Problematic Substrates
Schlüter-DITRA 25 matting is a membrane with a 3mm thick grid structure and is formed to be used as an uncoupling layer for problematic substrates. It is possible to overlay the d iffering floor substrates with this matting to eliminate stress cracks from lateral movement at their abutments, it may be needed to use a movement profile to alleviate any vertical movement. Besides, it can also be used to bridge screed cracks.
Moisture and flex affect particularly all types of wood or boarded floors. These floors needs to be overlaid with a minimum 18mm exterior grade WBP marine ply, treated against moisture absorption and screw fixed at 300mm centers across the board and 150mm centers along the edges in order to decrease the movement to a minimum. 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 25mm or over and 20mm exterior porcelain. 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 approximately). In these cases the paper face of the board should be sealed with a coat of Norcros Prime Bond mixed 1:4 parts water and allowed to dry, the tiles can then be fixed with a suitable Wall Tile Adhesive.
This substrate should be avoided in areas subjected to frequent wetting such as wet rooms/bathrooms.
Walls - Backerboard
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.
Norcros Pro Board is a waterproof construction/tilebacker board that can be used on walls & floors in a variety of situations. Its high density polystyrene core means that it can be used as an insulation board in conjunction with undertile heating.
Norcros Pro Board in a 10mm thickness will take up to 85kg/m², making it ideal for installation of heavy materials such as Splitface.
Walls - Plaster Skim
Gypsum plaster skim has an extremely low weight-bearing capability of only ≤20kgs/m², which generally precludes the use of natural stone tiles. Some of the thinner porcelain or ceramic tiles however are able to be fitted due to their low weight per metre square. Always check weights 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 neat Norcros Prime Bond 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 4 in 1 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, Norcros Pro Board, plasterboard or plywood (whichever is most appropriate for the environment) 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.
Consideration should always be given to the type of material to be used in wet areas. Natural stone is composed of many different minerals, all of which will react with moisture in different ways. This means that, over time, some colour change may occur and this possibility should be accepted prior to ordering or a porcelain alternative considered.
Tiles themselves will not form a waterproof layer, therefore all tiled areas that will be subject to any amount of water ingress, such as shower enclosures, wet rooms or stone showertrays should have a stable, waterproof substrate prior to fixing. This process is called tanking and prevents damage to the background of the installation. 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.
The tanking process is the same for installation of a tiled wet room or natural stone shower tray; due to the porous nature of stone, the substrate should be fully waterproofed.
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 an 800mm stainless steel linear grill.
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.
When using a stone showertray, our custom made showertray drain (sold separately) should be used in conjunction with the necessary tanking materials.
Showers should not be used for 14 days after grouting.
For more information please see our online guide Tiling to Wetroom & Showertray Installations.
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.