Tiling to timber floors with undertile heating
It is essential that the existing timber floor is level before proceeding and able to support the additional weight without excessive deflection. To increase the efficiency of the undertile heating, overlay the floor with Norcros Pro Board and fix either in a bed of Norcros Rapid Porcelain Adhesive or with suitable screw fixings (refer to Pro Board product data sheet).
** Green chipboard where a wax coating is present is not suitable as a tiling substrate.
The undertile heating cables/mat should be laid onto the boards in accordance with manufacturer recommendations. Encapsulate the heating cables in a layer of either Norcros PRO 10+. PRO 30 Fast Track Eco or PRO 50 Levelling Compound. This will protect the cables from damage. Allow to dry.
The general rule is to work from the centre outwards. Measure the width and length of the floor and draw a cross in the centre. From the central cross lay out the dry tiles allowing a 3mm wide gap between the tiles to allow for movement stresses within the floor during service. These gaps will be filled with grout once the tiles have been fixed and the adhesive dried. Make sure there are no awkward cuts, some adjustment may be necessary. Always be aware of how the floor will look when you enter the room.
To counteract movement stresses, which can result in tiles cracking and/or debonding, in accordance with British Standard BS5385-3:2014, movement joints should be provided:
a. Over existing and/or structural movement joints
b. Perimeter movement joints should be inserted at door thresholds and where the tiling abuts restraining surfaces such as perimeter walls, columns, curbs, steps and plant fixed to the base
c. Internal floors, which might be subjected to significant thermal changes, i.e. direct sunlight in atria, or underfloor heating etc, the floor area should be divided up by intermediate movement joints provided at 5m intervals in both horizontal directions to provide 25m2bays. N.B. These bay sizes may be increased to 40m2 when Norcros Permalayer anti-fracture matting is used.
Fix tiles in a highly polymer modified adhesive such as Norcros Rapid Porcelain Tile Adhesive Grey, Norcros Rapid Porcelain & Stone Adhesive White, Norcros Rapid Porcelain S1 Adhesive or Norcros Thick Bed Stone & Porcelain Grey/White or Rapid Porcelain S1 adhesive for large format tiles.
Using a suitable notched floor trowel held at a 45o angle, spread the adhesive onto the floor to form parallel ribs into which the tiles should be pushed with a firm twisting action, this will collapse the ribs of adhesive and produce a 3-4mm solid bed of adhesive beneath the tiles. Work in small areas and discard any adhesive that begins to dry or ‘skin over’. Tiles with deeply keyed back profiles may need to back buttered. Every so often lift a tile to check that it is in full contact with the adhesive and that no voids are left in the adhesive bed. Wipe off any adhesive residues from the surface of the tiles using a damp sponge before the adhesive sets. Remove deposits of adhesive which may build up in the gaps between the tiles.
DO NOT WALK ON THE TILES FOR AT LEAST 2-3 HOURS, or until the adhesive has set.
Floor tiles, especially natural stone and porcelain can be difficult to cut and good quality tools are required. These can bought or in some instances hired. A slide cutter and nippers are essential, however an electric wet cutter will make the job easier. For intricate cuts a cardboard template will help to achieve more accurate results.
Allow the adhesive to dry.
Use either Norcros Flexible Wide Joint Floor & Wall Tile Grout or Norcros 4 into 1 Grout. Clean out any dust, dirt and adhesive from between the tiles and make sure that the joints are dry.
Approximately 4-5 parts grout powder should be added to 1 part water, ensuring that the powder is added to the liquid to prevent the product from flash setting. Manually mix the grout to reduce the amount of air incorporated into the mix.
Holding a soft rubber grout float at 45o, sweep the mixed grout diagonally across the tiles, ensuring that the grout is pushed fully into the joints. Clean off as much grout from the surface of the tiles as possible and allow the grout to become touch dry.
Clean off the grout residues with a damp sponge wiped diagonally across the tiles. Allow the tiles to dry and buff the surface with a dry cloth.
Any stubborn residues may be cleaned off with washing up detergent mixed with warm water within 24 hours of grouting.
N.B. Before grouting commences trial a small inconspicuous area to check that the grout does not stain the tiles. If there is any risk of staining, the tiles should be fully sealed using a proprietary sealer before grouting begins.
N.B. The heating must not be switched on for at least 14 days after completion of tiling, raising the temperature gradually at a rate of 5oC per day.