Installation of natural stone tiles grouting

Installing

Pre-Installation

Stone tiles are quarried into blocks. These blocks are then milled in large factories using multi-million pound machinery. Most of these machines use water in the manufacturing process, with the tiles being packed immediately into crates once they’ve been manufactured. Tiles may well be wet when unpacked and can often appear darker in colour.


We recommend drying the tiles first. Once the tiles are dry the true colours and markings are then visible. This facilitates the even blending of the tiles to achieve the best look possible for your floor.  Also try and use lighting during the fixing process that represents similar lighting that will be utilised once the project is compete.


At this point you may find a tile or two that you don’t want to take centre stage of your floor. Use these tiles for cuttings or under units.


It is very important that all crates are opened and mixed prior to installation to ensure an even blend is achieved.


When laying stone in a pattern format a laying plan will be provided. This laying plan does not have to be followed, it is your decision. However, the tiles must be installed in the same ratios as the laying plan instructs. We are not able to sell patterns in single sizes; we only sell patterns in full and half modules.


Stone is a natural product and can be susceptible to minor damage such as edge/corner chipping when handling during the packing or unpacking process. This is normal in the industry and not a defect in the product. Industry practice is to utilise any tiles with minor damages for cuttings during installation. You may find a slightly higher ratio of minor damages when dealing with larger format tiles.


Although not always possible, we recommend dry laying as best practice. Dry laying allows the fixer to avoid any unsightly cuts, ascertain the optimum grout joints and work their way into an even blend.


Most of our tiles are calibrated to within +/- 1mm thickness. Occasionally some of our larger format tiles may not be calibrated and it is important that these tiles are graded. The chunkier tiles should be fixed first with thinner tiles being laid on top of a thicker bed of suitable adhesive to account for the difference in levels.


All surfaces that are to be fixed with stone should be flat, level, clean, dry & free of any grease or dust. It is important that the surface has minimal or no movement at all as this could cause problems later down the line.


Utilise our information sheets to ask your fixer a few important questions to see if you’re happy with their knowledge of natural stone fixing.

Substrates

Identifying the correct substrate is crucial for ensuring a suitable fixing procedure is followed. The materials required for preparation and fixing vary dependent on the substrate. Using the wrong fixing materials for the substrate can lead to numerous problems. All advice is only considered as a guideline and its important you consult with your screed supplier to ensure the correct screed is identified along with their recommendations prior to installation.

Sand & Cement

  • Sand & cement screeds are traditionally the most popular.
  • Not usually self levelling
  • Screeds do work with wet under floor heating systems but are susceptible to cracking. It’s always best to leave expansions joints in doorways and/or edge of the room. We would advise using our anti-facture matting in larger areas which greatly reduces the risk of cracks in the screed transferring through to the tiles.
  • Screeds don’t have to be primed before installation of tiles but it is recommended. Ensure screeds are dust free before priming/installation
  • Screed must be moisture tested and fully cured prior to tile installation.

 

Anhydrite (Gypsum)

  • Anhydrite screeds are usually self-levelling flow screeds
  • They are easier to install but take a bit longer to dry and require some more preparation work
  • Anhydrite screeds work well with under floor heating – we still recommend installing an anti-fracture matting.
  • Anhydrite screeds have a latence layer that rises to the surface which is weak and must be ground off
  • Anydrite screeds are gypsum based. Most adhesives are cement based and won’t adhere to gypsum. To avoid failures there are two solutions. Solution 1 is to prime the floor with a suitable primer, such as Kerakoll Primer Eco A; two coats are require at a criss –cross to each other. Solution 2 is to use a gypsum based adhesive. Gypsum based adhesives are more expensive than cement based adhesives so usually priming is the most cost effective option.
  • Screed must be moisture tested and fully cured prior to tile installation.

 

Wooden Floorboards

  • Wooden floor boards often have quite a lot of vertical movement and it is important that this is minimised. Non-stable floors can lead to cracking of the tiles/grout.
  • We’d recommend using marine plywood or tile backer boards to create a stronger, rigid substrate.
  • These are usually screwed down to your joists every 2-4 inches to minimise as much movement as possible.
  • You may or may not need to prime the substrate depending on which material has been used to reinforce the wooden floor.
  • Similarly, depending on how much vertical movement is left, you may or may not decide to add a latex additive to your flexible adhesives and grouts to allow for extra flex.
  • Anti-fracture matting is not designed to protect against vertical movements, only horizontal movements.

Adhesive

Adhesive

  • Natural stone should not be spot fixed but laid on a full, solid bed of adhesive. Spot fixing can leave marks on the stone tile surface.
  • To ensure an even adhesion, large format tiles may need to be ‘butter-backed’ first. This also applies to travertine tiles which may contain voids.
  • We advise fixing all natural stone tiles with a white adhesive. The reason for this is to avoid any mineral reaction or pigmentation bleed which could cause a chemical reaction and undesirable markings.
  • We always advise using a flexible white adhesive when installing natural stone tiles.
  • Ensure that you clean off any adhesive the lands on the tile surface with a damp sponge as you go.
  • A latex additive can be added to the adhesive if extra flex is required due to wooden substrates.

Levelling

A degree of variation in dimensions within Porcelain tiles is to be expected, due to their nature and production. This is often more noticeable on larger format tiles. In order to avoid emphasising this, joints should be staggered by a maximum of 20-30% of the length. It is also standard practice to use levelling wedges and spacers when tiling, in order to create a flat and level floor. Should you have any queries, please speak to one of our team or discuss with your tiler.

Grouting

Grouting

  • All tiles must be grouted. The thinnest grout joint achievable is around 3mm. Grout joints are important as stone tiles are calibrated to within +/- 1mm
  • Tiles that are not straight cut (e.g. tumbled) may yield a slightly wider grout joint
  • Grout joints can slightly vary in width across a floor. This is especially true when fixing a pattern format with mixed size tiles and is perfectly normal. Dry lay first so you can work out the best way of laying.
  • Please consider what colour grout to use before fixing. If you decide to go for a white grout then we recommend using a white coloured adhesive to avoid any ‘shadowing’ effect – the undertones of the adhesive colour showing through the grout.
  • We always recommend using the same manufacturer for your adhesives and grouts. Make sure grout joints are dry and free of dust & dirt prior to grouting. Always follow the product specification sheet when installing.
  • Ideally, when grouting tiles should be ‘pointed’. If laying a travertine or another material that has natural pitting or voids that you’d like to fill then we recommend ‘slurry’ grouting. This is a messier process and it is important that all grout residue is removed from the surface of the tile.
  • Grout-and-clean: Grout residue on the surface of the tiles must be cleaned as part of the grouting process. We recommend cleaning the floor thoroughly and allowing time to fully dry before sealing. MN Power-Clean can be used to remove any grout residue that has dried on the surface of the tile. Please bare-in-mind that grout residue left on the surface of the tile for too long can be very difficult to remove.
  • It is best practice to apply a coat of sealant to the tiles after installation but prior to grouting. This is to avoid any pigmentation being absorbed by the stone tiles and avoids potential discolouring. Ensure that the edges of the tiles are also sealed (NOT the back of the tile). Follow the adhesive specification if unsure.
  • Sealing the edges of the tiles avoids any undesired pigmentation absorption – this can result in ‘picture framing’. We also recommend choosing a grout colour lighter than the colour of the stone for the same reason. Always test on a small area first to see if there is any reaction.
  • A latex additive can be added to the grout if extra flex is required due to wooden substrates.

Sealing

Sealing

  • All natural stone must be sealed
  • We recommend Lithofin Stain Stop MN which is an impregnating sealer sitting just below the surface of the stone. It is a matte sealant with minimum alteration to the appearance, leaving the stone looking as it was intended to after manufacturing.
  • Lithofin Stain Stop MN repels water, oil and grease.
  • Some sealants can leave an artificial sheen to the surface of the tile.
  • It is possible to use a colour intensifier in conjunction with a sealer to draw out bolder colours.
  • We recommend sealing the tiles after initial fixing.
  • Tiles must be clean and bone dry prior to sealing
  • We recommend a further seal after the grouting process which will add protection to your grout too. Again, tiles must be clean and bone dry.
  • It is important to seal the edges of the tiles prior to grouting as this helps prevent against pigmentation bleeding resulting in picture framing (a darker outline around the edge of the tile)
  • Sealant will usually last approx 4-6 years before a top-up coat is require. In high water traffic or outdoor areas this may need to be adjusted to once every 6-12 months.
  • Sealant can’t protect against acidic reactions. If any strongly acidic liquids are dropped onto the surface of the stone it is recommended to neutralise them with water and clean as soon as possible.
  • Sealant acts as a first line of defence. Eventually, if left uncleaned, the sealant can be penetrated and in worst case scenarios the stone stained. The sealant does a great job but, if you spill something like coffee onto your floor it is advised you clean it up before heading off on a weekend break!