Wood moves, bends, bows, stretches and shrinks – and this makes it one of the most difficult substrates on which to tile. In comparison to this, ceramic tiling is a rigid material and stress between the movement of the wood and the ceramic tile can cause failure of the tiles to grip to the substrate or form cracks.
Wood comes in many forms – plywood, particleboard, wood composites and floor boards and the type of wood will affect the preparation and adhesive used. For all wooden floors, because tiling effectively seals the top surface of the floor, adequate under-floor ventilation is essential if rot is to be avoided.Do not tile floating chipboard floors.
Floorboards
Preparation technique
Ensure boards are screw-fixed and rigid and free from grease and dirt.
Once boards have been fixed, allow them to reach equilibrium with to the ambient humidity and conditions in the room to reduce the possibility of warping.
For tongue and groove boards, screw at a minimum 300 mm centres and two screws per board to the joist, avoiding pipework and electrics.
Prevent water ingress to the installation at all times and, where necessary, use a tanking system such as PCI’s Lastogum X in conjunction with an overlay.
Adhesive application
Timberflex from PCI will perform better on wood than a general purpose adhesive, even if the later is incorporated with admixtures.
Timberflex allows horizontal and lateral movement in the floor, but if the vertical deflection is great enough the adhesive will remain bonded but the brittle tile surface may crack.
A supplementary tactic is to lay a sheet of external grade plywood (WBP),marine plywood, or PCI’s Pecidur tile backer board, as a secondary substrate to stiffen the floor and to separate the tiles and their bed from the original wooden floor.
Grouting
Once the adhesive bed has set, grouting may commence.
A polymer-modified grout such as Groutfast 20 Rapidflex is recommended because it offers a degree of resilience to movement.
Drying times will depend on the varying conditions of the site.
Movement Joints
Please refer to Special Situations Bulletin 1 due to the complexity of this subject.
Plywood
Preparation technique
External grade plywood (WBP), of a thickness15mm-18mm, is often used to cover sub-standard substrates or floorboards.
Securely fix the plywood to the substrate with screws at maximum centres of 300 mm, through to the joists and avoiding pipework and electrics, to prevent any deflection in the floor which could result in cracked tiles.
Seal the back of the plywood and the edges (as per British Standard requirements BS 5385: Part 1: 3.1.2.6) with a neat application of PCI’s Primer W.
Before tiling, allow the fixed boards to reach equilibrium with the ambient conditions of the installation so as to prevent warping.
Ensure that there is adequate under-floor ventilation to prevent warping and rot once tiles are laid and the top surface is sealed.
There is no need to prime the substrate surface.
In wet areas, the plywood should first be tanked-out with a tanking system such as PCI Lastogum X or Seccoral 2K.
Adhesive application
For rigid substrates, use an adhesive such as PCI’s WF1 wall and floor adhesive, or for substrates showing some deflection use a flexible adhesive such as PCI’s Timberflex. Flexible adhesives are designed to accept lateral, horizontal,movements in floorboards but can not withstand excessive deflection which may cause the rigid tile surface to crack.
Drying times for the installation will depend upon the varying ambient conditions of the site.
Grouting
Once the adhesive bed has set, grouting may commence.
A polymer-modified grout such as Groutfast 20 Rapidflex is recommended because it offers a degree of resilience to movement.
Drying times will depend on the varying conditions of the site.
Movement Joints
Please refer to Special Situations Bulletin 1 due to the complexity of this subject.
Chipboard and other wood composites
Preparation technique
Reduce deflection of the chipboard or composite floor (and thus cracked adhesive and tiles) by screwing down the boards at maximum centres of 300 mm, and through to the joists, avoiding pipework and electrics.
Seal the back of the chipboard or composite floor (as per British Standard requirements BS 5385: Part 1: 3.1.2.6)with a neat application of PCI’s Primer W.
Allow the fixed boards to reach equilibrium with the ambient conditions of the installation before tiling, to prevent warping.
Ensure that there is adequate under-floor ventilation to prevent warping and rot once tiles are laid and the top surface is sealed.
To increase the stability of the floor, overlay the boards with exterior grade plywood (a thickness of less than 18mm may be suitable, such as PCI’s Pecidur tile backer boards), screwed down at 300mm intervals (for treatment and handling of plywood, please refer to the Plywood preparation section.
In wet areas, the plywood should first be tanked-out with a tanking system such as PCI Lastogum X or Seccoral 2K. Or, alternatively PCI Pecidur is a waterproof substrate which can be used as an alternative to wood to construct walls and surrounds.
Adhesive application
For use over timber or PCI’s Pecidur tile backer board, apply a flexible adhesive such as PCI’s Timberflex or Tilefast 6 Flex for wet applications, such as showers.
Flexible adhesives are designed to accept lateral, horizontal,movements in floorboards but can not withstand excessive deflection which may cause the brittle tile surface to crack.
Drying times for the installation will depend upon the varying ambient conditions of the site.
Grouting
Once the adhesive bed has set, grouting may commence.
A polymer-modified grout such as Groutfast 20 Rapidflex is recommended because it offers a degree of resilience to movement.
Drying times will depend on the varying conditions of the site.
Movement Joints
Please refer to Special Situations Bulletin 1 due to the complexity of this subject.
For more information, contact PCI’s Techincal Services Department on 0161 794 7411