Stone & Porcelain Installation
The correct installation of your chosen material is of equal importance as choosing the product itself. This section provides only general information on fixing, as it is impossible to provide a single guide due to the variety of factors which need to be considered, when specifying adhesives, grouts, sealants or other specialist ancillary materials.
If you require a quotation then please furnish us with any necessary information 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 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 or gypsum-based tile adhesives are the most appropriate for this method. Some travertine or large format tiles may have to be ‘buttered’ with adhesive on the back in order to ensure complete adhesive coverage.
Tiles should occasionally be lifted during the laying process to ensure that sufficient compaction and full bed adhesion is being achieved.
Fast setting adhesives are advisable in order that the moisture disperses quickly from the Stone or Terracotta. This helps to prevent various reactions that could be caused by the moisture retention of the tile.
Standard setting adhesives have a longer working time, thereby, allowing more time to make minor adjustments during the installation process, ideal for 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.
Light materials generally require fixing with white adhesives to prevent possible discolouration should the alkaline mortar bleed into, or react with the minerals within the body of the stone itself and also to prevent shadowing through to the associated light coloured grout.
Flexible adhesives, combined with further substrate preparation, are required 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.
For uncalibrated Stone tiles, the appropriate Large Format Flexible Floor Adhesive, such as Norcros Thick Bed Grey Flexible Adhesive should be used to accommodate the variation in tile thickness and associated increase in adhesive bed thickness. This will be most noticeable if laying a mix of sizes in an uncalibrated material.
Grout & Silicone
Grout joints are in place to allow for any movement of tiles and should be a minimum of 3mm; it is not possible to ‘butt-joint’ tiles with the exception of Splitface materials which are designed to be fitted this way, although some grouting may be required dependant on the situation.
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.
Grouts are available in a variety of 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 grout.
Some materials require the use of specific grouting materials, such as Norcros 4 into 1 Grout. Please contact your nearest showroom for specific advice.
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 Norcros Flexible Wall & Floor Grout or Norcros 4 into 1 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, Flamed and 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 after grouting but before additional sealing. Any grout residue left on the surface may prove difficult to remove if left too long.
Norcros 4 into 1 grout contains an anti-bacterial agent to resist mould so is ideal for 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 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
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 & Splitface 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 Norcros Pro 30 Fibre Levelling Compound or alternatively a Large Format Flexible Floor Adhesive, such as Norcros Thick Bed Grey, can be used 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 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.
The surface of the screed should then be sealed with progressively stronger coats of Norcros Prime Bond prior to fixing of tiles. The initial coat should be diluted 1:4 with water and allowed to dry; the next coat should be diluted 1:3 and applied to the surface at 90° to the previous coat. If the screed is still absorbent then a third coat diluted 1:2 should be applied at right-angles to the previous.
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
This is usually an electric mat or cable system which should be suitable for use with natural stone, porcelain or ceramic flooring. The heating mat should be bedded into a layer of Pro 30 Fibre Floor Levelling Compound. This protects the heating elements from any damage during the fixing process.
Schlüter-DITRA 25 matting should be installed on to the Pro 30 Fibre Floor Levelling Compound to effectively isolate the tile covering from the heated substrate, thus preventing stresses from damaging the tile surface. Schlüter-DITRA 25 matting will not inhibit heat transfer or reduce the efficiency of the heating system.
Floors - Timber
Wood or its man-made derivatives (chipboard/plywood/T&G/floating timber floors) will be subject to movement under load, temperature and humidity. Rigid tiles cannot absorb deflection or compression and will break or de-bond away from their substrate, so measures should be taken to ensure that the receiving substrate is suitably resistant to moisture and movement in order to prevent deformation and subsequent de-bonding.
These timber substrates cannot be tiled onto directly and should be overlaid with 18mm exterior grade WBP plywood. The ply should be allowed to acclimatize for several days on site prior to being suitably sealed on the back, face and edges with neat Norcros Prime Bond. Cross joints should be staggered, and a gap of 1-2mm should be allowed between sheets. Boards should be fixed with countersunk screws at 300mm centres in both directions across the face of the board and 150mm centres along the board edges. If ply is to be laid directly onto joists, then a greater thickness may be required.
Schlüter-DITRA 25 matting uncoupling membrane which will serve to counter any lateral movement present within the floor should also be installed. This should be fixed with flexible tile adhesive using a 3-4mm notched trowel and thereafter a maximum of a 10mm flexible adhesive bed is applied over the mat to embed the tiles.
As an alternative to ply, a suitable construction board such as Norcros Pro Board can be used to overlay. This will generally be thinner than ply and so bring the overall construction height down whilst offering improved stability.
If the area will be subjected to frequent wetting (such as a wet room) then a suitable water resistant or waterproof construction board should be used.
To test a floor for ‘bounce’, fill a glass or bowl completely with water until the ‘meniscus dome’ is apparent on the surface, then walk around the floor and check for spillages. If spillages occur then additional preparation of the floor will need to be undertaken.
Floors - Existing Tiles
Any loose tiles should be removed and the floor degreased and thoroughly cleaned prior to fixing.
Vinyl tiles will require sealing with neat Norcros Prime Bond prior to fixing with suitable adhesives.
Glazed tiles require a slurry bonding coat (made up of 2 parts any adhesive or Floor Levelling Compound to 1 part Priming Agent), to provide a key for fixing with Rapid Flex S1 Wall & Floor or Large Format Flex Floor Adhesive. This coat can be brushed onto the existing tiles and allowed to dry (1 hour approx) before fixing.
Unglazed tiles or natural stone that have been thoroughly cleaned can be adhered to with any suitable adhesive without remedial action.
Floors - Movement Joints
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
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 minimum 18mm exterior grade WBP marine ply, treated against moisture absorption and 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 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 approx). 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 - Plywood
18mm exterior grade WBP plywood can be used and should be sealed on all sides/faces with Norcros Prime Bond before being suitably batten fixed with vertical and horizontal wooden supports at 300mm centres and screwed firmly at 150mm centres at all joints and edges, this is generally capable of taking ≤30kg/m² approx.
If fixing in areas subjected to frequent wetting it is preferable to substitute for a suitable tile backer board.
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.