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The fixing and sealing of your stone is as important as choosing the stone itself. The advice given by Mandarin Stone is supplied in good faith and is to be used as a guide and general overview of the fixing and sealing of stone. Advice should also be taken from the professional who is fixing your stone.
Mandarin Stone can only advise on the fixing and sealing of products that we offer, for example Norcros Adhesives, FILA sealants and Schlüter-Systems. We know they are compatible with our stones and can provide technical data sheets on such products. Where alternative products are being used their compatibility should be checked with the manufacturers/suppliers before use.
- Cement based tile adhesives are most appropriate for stone installations using the solid bed method.
- Fast setting adhesives are advisable in order that the moisture disperses quickly from the stone or terracotta, to prevent various reactions that could be caused by the moisture retention of the tile.
- Light stones require fixing with white adhesives to prevent possible discolouration should the alkaline mortar bleed into or react with the minerals within the stone body itself.
- Flexible adhesives are recommended when the substrate is wood, existing glazed tiles (floor application only) and underfloor and/or undertile heating is present.
- For uncalibrated tiles, the appropriate Norcros Thick Bed Flex Floor Adhesive should be used.
- Cement based grouts are most appropriate for stone jointing. Stones with a textured surface tend to have grout joints of 6-10mm, whereas smooth honed and polished stone joints can be 3-5mm.
- 'Slurry' grouting with the appropriate coloured Norcros Wall & Floor Grout is necessary with unfilled travertine and some limestone in order to fill naturally occurring pits and crevices.
- Norcros Adiflex Grout Additive is to be added to the grout whenever a flexible adhesive has been used to fix the tiles.
- All stones and terracotta tiles should be treated prior to grouting as some tiles may absorb pigments from the cement grout.
- All natural stones and terracottas are porous and require varying degrees of impregnation, i.e. a base coat application, to quell the porosity of the tile. Further surface sealing is then required to protect, maintain and provide a finish to the tiled wall or floor.
- We recommend that most natural tiles should be fixed (but not grouted) clean and dry prior to any treatments being applied. An exception would be unfilled travertine as the cement grout needs to fill up and adhere into the natural pits and the impregnation process inhibits this process to a certain degree.
- Impregnation, if applicable to the stone type or finish, is the first treatment and the number of coats applied will depend on the porosity of the stone. Applications must continue until the tile has virtually reached 'saturation point' and any impregnator residues must be cleaned off the tile surface immediately.
- Tiles then undergo the grouting process and further applications of the impregnator can be applied to the grout joints and tile surface. Any residues must be cleaned off the tile surface immediately.
- After grouting, surface sealing and/or waxing is then necessary with a choice of either a matt, satin or shiny surface finish. Atleast two coats are normally applied but this will depend on the finished 'look' required. ach coat should be allowed to dry before the next application.
- All installations need a certain degree of cleaning and maintenance determined by their frequency of use.
- Heavily trafficked or used areas are more likely to require re-application of treatments,especially if the stones look dull or show surface wear.
- All abrasive cleaning detergents should be avoided as they remove the surface sealant.
- Incorrectly applied impregnators, sealants and staining problems all have their antidotes. Please refer to the Ancillary Product section for more information.
- Stones are often packed very tightly and are wet at the point of production and are unable to dry out until unpacked. They will often lighten in colour as they dry and 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 batches of stone are shuffled to ensure evenness in distribution of any such variation. This will mean opening all crates or pallets of materials supplied.
- Minor damage such as edge chipping is often caused in packing or unpacking tiles but it is deemed normal practice for these to be used as cuts during the installationprocess.
- Uncalibrated tiles need to be graded prior to installation; the thicker tiles will dictate the floor level and should be installed first.
- Dimensions listed are nominal as slight variation in size and thickness can occur with most natural material.
- A dry level screed is an ideal fixing substrate. New screeds usually need to ‘cure’ or dry out at a minimum of 1 week for every 25mm of screed depth.
- Schlüter-DITRA, is an uncoupling membrane which can be installed on a drying screed as it allows moisture in the substrate to evaporate through its air channels, thus neutralising vapour pressure.
- Uneven floors can be overcome to a certain extent with Norcros Universal Levelling Compound, alternatively use Norcros Thick Bed Flex Floor Adhesive for fixing which can be used to a maximum bed thickness of 25mm.
- These must be cured to their respective manufacturer's recommendations before tiling can begin as they retain moisture for longer periods than conventional sand and cement screeds or use Schlüter-DITRA to neutralise the vapour pressure.
- This is usually a water piped system which is installed in a minimum screed depth of 65mm, above the pipes, in accordance with British Standards. After the screed has ‘cured’ it should be heated gradually to manufacturer’s recommendations and then allowed to cool down completely before fixing floor tiles. If the screed cannot be heated prior to tiling or the screed has developed stress cracks, Schlüter-DITRA 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.
- This is usually the electric mat or cable system and can be tiled directly over with suitable Norcros tile adhesive. Alternatively prior to tiling the electric mat can be bedded into a screed of Norcros Universal Floor Leveller. This latter method prevents damage to the heating elements during the laying process.
- Schlüter-DITRA can be installed above the mat to effectively isolate the tile covering from the heated substrate, thus preventing stresses from damaging the tile surface. Schlüter-DITRA will not inhibit heat transfer
or reduce the efficiency of the heating system.
- 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.
- To test a floor for 'bounce', fill a glass completely with water until the 'meniscus dome' is apparent on the surface, then walk around the glass and check for spillages.
- If spillages occur then remedial action needs to be taken. Install an overlay of 18mm exterior grade WBP plywood with staggered joints, suitably sealed on its back, face and edges with Norcros Prime Bond and screwed down at 300mm centres and 150mm centres along the board edges.
- Alternatively, or as well as, install 3mm Schlüter-DITRA which is an uncoupling, antifracture membrane. 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.
- Any loose tiles should be removed and the floor degreased and thoroughly cleaned
prior to fixing.
- Vinyl tiles will require sealing with Norcros Prime Bond prior to fixing with Norcrosadhesives.
- Glazed tiles require a slurry bonding coat (made up of 2 parts any Norcros adhesive or Norcros Universal Levelling Compound to 1 part Norcros Prime Bond), to provide a keyfor fixing with Norcros Rapid Flex or Thick Bed Flex Floor Adhesive. This coat can be brushed on to the existing tiles and allowed to dry before fixing.
- Unglazed tiles or natural stone can be adhered to with any Norcros adhesives without remedial action.
- Schlüter-DITRA is a polyethylene 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 at their abutments; it can also be used to bridge screed and masonry cracks.
- All types of wood or boarded floors are particularly affected by moisture and flex. These floors should be treated against moisture absorption and firmly fixed to its substrate by placing screws at appropriate close intervals to minimise flexibility. Schlüter-DITRA serves as a waterproof membrane and as a vapour pressure equalisation layer to accommodate moisture occurring at the underside. It also uncouples the floor covering from the substrate and prevents the transfer of stresses or flex to the tiled surface.
- 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 and providing the substrate is sufficiently load bearing, the tile covering can be installed immediately.
- 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 Norcros Tile Adhesive. To accommodate 20mm thick stone (>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.
- Plasterboard that has not been skimcoated with a finish coat of plaster will take most 10 and 12mm stones (>32kg/m2 approx). In these cases the paper face of the board should be primed with Norcros Prime Bond 1 : 4 parts water and the tiles fixed with Norcros Tile Adhesive.
- Hardibacker is a cement based, water resistant tile backing board. This is available in a 6mm or 12mm thickness and when suitably screw fixed, provides a load bearing facility of >35kgs/m2, which is an adequate load bearing substrate for stone tiles up to 15mm in thickness.
- 18mm exterior grade WBP plywood can be used and should be sealed on all sides/faces with Norcos Prime Bond before suitably batten fixed with vertical and horizontal wooden supports at 300mm centres and screwed firmly at all joints and edges.
- These are not deemed suitable substrates as they do not have the weight bearing capacity required for stone tiles.
- If the underlying substrate is capable of supporting the installed load then Hardibacker, plasterboard or plywood should be suitably primed, where necessary, then screw fixed to apply the stone tiles.
- 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 30-40mm of a sand bed being compressed with a vibrating plate compactor. This then enables a wet or semidry mortar bed, dependant on stone thickness, to bed the stone flags or cobbles in.
- The correctly prepared substrate will support all exterior stone tiles, immaterial of their thickness
- All tiled areas that will be subject to any amount of water ingress should have a waterproof substrate prior to fixing. This can be achieved with Schlüter-DITRA and/or KERDI membranes.
- Schlüter-KERDI 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, loadbearing, non-flexible substrate with a thin bed adhesive and with 50mm overlapping joints to form a complete watertight surface.
- Schlüter-DITRA is a waterproof polyethylene membrane with a grid cavity structure and an anchoring fleece on its underside. It can be adhered to its substrate using a thin bed adhesive. This adhesive can also be used to install the Schlüter-KERDIKEBA which makes the matting watertight. When using Schlüter-DITRA the tile dimensions should be a minimum of 50x50mm.
- Schlüter-DITRA is flexible and serves a dual purpose for wood floors, firstly as a waterproofing membrane when the mat joints have been sealed with Schlüter-KERDIKEBA, secondly as an uncoupling or separating membrane between the floor and the tiled surface above to prevent stress cracks.
- Schlüter-KERDI-DRAIN is a floor drainage system for installation with Schlüter-KERDI or DITRA and/or other bonded waterproof membranes. Floor drains with either 150x150mm or 100x100mm stainless steel grates are available.
- 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 be installed unless the distance between restraining surfaces is less than two 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 8-10 metre centres in each direction. Over potentially flexible type substrates and underfloor heating, movement joints should be positioned at 6 metre centres in each direction. Additionally movement joints should be placed directly over supporting walls or beams.
- All existing movement joints in the base 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, etc.
- Horizontal movement joints should be positioned at floor and ceiling positions.
- A wide range of movement and control joint profiles are available from Schlüter Systems.
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