Tiling to lightweight / medium density blockwork walls
Lightweight and medium density blockwork have a compressive strength of less than 7N/mm2 and are suitable to receive a tiled finish in internal, dry installations as long as they are sufficiently flat and fair faced. Externally, in internal areas which may be subject to moisture or in instances where the blockwork is not deemed to be sufficiently flat, it would need to either be over boarded with Norcros Pro Board or would require the application of a cement: sand render coat.
The blockwork must be a minimum of 6 weeks before either the application of a cement: sand render coat or tiles. It must be clean, dry and free from dust, laitance or any contaminants which may act as a release agent and prevent the adhesive from bonding to the blockwork. Once dry, the clockwork should be primed with Norcros Prime Bond diluted 1: 4 with water which should be allowed to dry.
Tiling should be set out from the centre of the walls, either the centre of a tile or the joint between two tiles positioned in the centre of the wall, whichever of these two options avoids small cuts of the tiles. Make a gauge rod using a length of straight timber. Along the length of the timber mark out the width of the tiles, leaving a gap at least 2mm wide between each tile. Set out the horizontal position of the tiles so that the same size cuts are made at either side of windows etc. avoiding any small cuts. At the lowest point of the wall to which tiles are being fixed, such as the skirting board, work surface etc. place an uncut tile and draw a line along the top of the tile. Nail a batten below this line, using a spirit level to make sure that it is level. The first line of tiles will rest on this batten. Measure the width of the wall and mark the centre point. Draw a vertical line at this centre point using a spirit level to make sure that the line is straight. Start tiling at the centre point.
To counteract movement stresses, which can result in tiles cracking and/or debonding, in accordance with British Standard BS5385-1:2009, movement joints should be provided:
- over existing and/or structural movement joints
- where tiling abuts other materials and at junctions between different substrates
- at vertical corners
- at 3m to 4.5m centres both horizontally and vertically and in areas where stresses are likely to be concentrated such as at changes of alignment.
- An increase in the frequency of movement joints should be considered if large degrees of thermal movement or vibration are expected within an installation.
More information on the provision of movement joints is available in the Norcros How to Sheet ‘Movement Joints in Tiled Installations’.
Some porcelain & natural stone tiles 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.
Tiles should be fixed in Norcros One Part Flexible Tile adhesive or Norcros Standard Set Flexible S1 adhesive. Norcros Rapid Porcelain Tile or Rapid Porcelain S1 adhesive may be used if a rapid setting adhesive is preferred. Mix the adhesive in accordance with the mixing instructions on the bag.
Using a suitable notched wall trowel held at a 45o angle, spread the adhesive onto the wall 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 2-3mm 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. In areas subject to wetting such as showers, it is essential that a solid bed of adhesive is achieved beneath the tiles. 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.
Allow the adhesive to dry.
Use Norcros Wall Tile Grout. In areas subject to wetting or where movement/vibration is antic-ipated Norcros Stop Mould Grout, Norcros 4 into 1 Grout or Norcros Super Epoxy may be used.
Clean out any dust, dirt and adhesive from between the tiles and make sure that the joints are dry.
Mix the grout in accordance with the recommendations on the packaging.
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.