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.
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 and 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.
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, & Porcelain tiles.
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 & 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 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.
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.
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.
Uneven floors can be overcome to a certain extent withFibre Levelling Compound or alternatively a Large Format Flexible Floor Adhesive, such as Thick Bed adhesive, 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%.
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 Primer 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).
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 Fibre Reinforced Floor Levelling Compound. This protects the heating elements from any damage during the fixing process.
Floors - Timber
Wood or its man-made derivatives (chipboard/plywood/T&G/
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 Priming 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.
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 Priming 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
If using DECOUPLING MAT 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 matting and providing the substrate is sufficiently load-bearing, the tile covering can be installed immediately.
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.
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 PRIMER usually 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 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 - Plywood
18mm exterior grade WBP plywood can be used and should be sealed on all sides/faces with Primer 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 PRIMER 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.