Tiling onto a floating chipboard floor

Floating timber floors are generally constructed of a timber base into which a dense acoustic or insulation material is laid (approximately 50mm thick). Tongue and groove timber boards, generally flooring grade chipboard, are loose laid on top of the insulation to provide a base to receive floor coverings and/or finishes. Heating pipes may be bedded in the insulation layer. Normal wooden floors will flex when walked upon but this movement is even greater on a floating floor as the boards are not supported by joists.

In this article we discuss tiling on chipboard.

Tiling onto chipboard can be problematic for a couple of reasons, movement and water damage.

Chipboard flooring is renowned for flexing, often not being screwed in well, these combined means that the boards move. Known as deflection, this is where the boards bend between the joists or the joists themselves flex when you walk over them, this is usually the reason for cracked tiles.

Secondly, once chipboard gets wet it swells and disintegrates, in turn lifting your tiles. For this reason, chipboard should never be used in a wet room or any other constantly wet area. We’d always recommend over boarding and if movement is an issue, a decoupling membrane.

Read on for a step by step guide to tiling on chipboard flooring.

Measure the length and width of each area you are going to tile with a tape measure, multiply the two sizes together and you will get the number of square meters you will need. For irregular shaped rooms, divide the area up into different segments to work out individually, and then add together. Remember to allow for an extra 10% for any breakages, cuts and wastage. If you are tiling in a brick bond pattern then 10-15% is advised.

If you are unsure just take your measurements (height and width) of each wall you are tiling into your local store who will be happy to help and give any advice you may need for your project. Alternatively, try our online tile calculator.

The biggest problem when tiling on a floating floor is that the floor will be moving up and down, this is called deflection, a slight spring or bounce can be felt as you walk upon this type of floor. If this movement isn’t corrected before tiling then there is high risk of the grout cracking or falling out of joints or tiles lifting and cracking.

If the structure is considered to be sufficiently free from deflection, the floor will be deemed suitable to receive a tiled finish. To check the rigidity of the floor, a container should be filled to the rim with water and placed in the centre of the floor. Standing approximately one metre away from the container, jump up and down on the floor. If the water spills out of the container then the floor requires strengthening.

It should be noted however that in some installations, even when strengthened with an overlay or an anti-fracture/decoupling membrane, a floating floor may still not be able to support the additional weight of tiling without excessive deflection.

Verify that the extra height from the over boarding can be accommodated and that the floor is capable of supporting the expected load. Use WBP grade plywood at least 15mm thick, the thicker the better, before laying the boards. You will need to seal the back face and edges with undiluted BAL Bond SBR.

Lay the boards so that the joints do not coincide with joints in the existing timber and leave a slight gap between boards to allow for expansion. Screw the boards down at 200 to 300mm intervals. Do not use nails as the movement of the floor can work the nails free and cause issues down the line. Leave a movement joint around the perimeter for expansion.

Once again check the movement of the floor using the above deflection test to ensure the substrate is stable enough to prevent problems further down the line.

A good idea is to add an anti-fracture/decoupling membrane such as Durabase or BAL Rapid Mat.

The general rule of tiling a floor is to work from the centre outwards so the main aim is to make sure the centre of the floor is positioned correctly. From there you can extend the tiling pattern towards the edges of the room.

Measure the opposing walls, mark the centre of each and draw a line using chalk or pencil between the two points. Repeat for the other two walls and you will have found your centre point of the room. Bear in mind that rooms aren’t always perfect squares so start as centrally as you can.

From the centre of your room, dry lay a row of tiles in the four directions up to the walls. Make sure you include (a minimum of) 3mm tile spacers so that the joints are even. If there is only a thin piece of tile left at a wall, move your centre tile around slightly until there’s a gap of roughly the size of half a tile around the edge of the whole room. Once you are happy, mark the centre tile with chalk or pencil.

Make sure you plan ahead so you are able to exit the room without stepping on any tiles as they won’t have set. If the room is essential, you can tile half of the room at a time, so you are still able to access the room.

Mix the recommended tile adhesive in a mixing bucket as per the instructions on the bag. We recommend you only use BAL Single Part Fast Flex on a floating floor due to it being a rubber/cement based product giving it a rubber like flexibility.

If you don’t wish to add an anti-fracture matting such as Durabase or BAL Rapid Mat then you can use BAL Single Part Fast Flex adhesive along with a DEX Tipped Notch Trowel. This creates a solid bed of adhesive under the notches which enables it to act in the same way as anti-fracture matting. If you decided to use an anti-fracture membrane then use BAL Single Part Fast Flex with a normal notched trowel, the size of which depends on the tile size.

Working off your set out lines and/or from a straight edge, spread the adhesive on the floor, holding the notched trowel (minimum 8-10mm notched size) at a 45° angle and drag across the floor spreading evenly, ensuring the notches are in the same direction. Only cover a small area at a time, approx. 1m², as the adhesive will dry on the surface.

Place the tile on the bed of adhesive, press down with a twist and slide into place to ensure the adhesive sticks properly (for larger tiles, it may require a thin layer of adhesive on the back of the tile as well as the floor).

Put the spirit level or your straightedge on the tile in both directions to ensure it is even and flat then insert a tile spacer in between each tile. Be sure to press the spacers well below the surface of the tile so that they’ll be hidden once your floor is grouted. Remove any adhesive from the tile face with a damp sponge as you go along as it’s much harder to remove once set.

A manual cutter can be used for straight cuts and an electric cutter for right angles, curved edges and thicker tiles such as porcelain and natural stone. See here our basic guide for cutting tiles.  

When grouting tiles laid over timber, you should make the same considerations when choosing your grout as you do when choosing your adhesive. Consider the need for flexibility to cope with the additional movement faced when tiling onto a floating floor.

We would recommend a product like BAL Micromax3 with BAL Admix GT1 pre-diluted 1:2 by volume with water when used with BAL Single Part Fast-Flex.

Before grouting, check the potential staining risk. You can do this by applying grout to a few leftover tiles or offcuts. If discoloration occurs or difficulties are encountered with cleaning off any surplus grout, apply BAL Protective Sealer and repeat the trial.

Tiling in hot and humid weather will dramatically alter the setting times so always mix up small quantities, grout and clean off a little at a time in warmer conditions.

Remember not to grout the perimeter joint of the room, complete the job by sealing the perimeter movement joints with BAL Micromax2 Silicone sealant, colour matched to the BAL Micromax3 grout.

Mix water and grout powder in a mixing bucket as instructed on the packaging bearing in mind not to mix too much as it will harden quickly. Always mix to the instructions on the bag as different grouts require differing quantities of water.

Place some grout on the tiles, hold the grout float at a 45° angle and apply the grout ensuring all the joints are filled. Once all the joints between the tiles are grouted (working in small areas), allow approx. 15 minutes for the grout to be touch dry (at 20°C). Using a dampened sponge, clean the surface diagonally to the grout lines. Rinse out the sponge frequently with clean water.

Don’t put too much pressure on the grout joints and don’t over wash them as you will remove the pigment out of the surface of the grout and white areas will appear. If you have over washed this can be easily solved by gently sanding off the top layer of the grout with fine sandpaper.

Allow approx. 60 minutes for the grout to set sufficiently within the joints then polish the tile’s surface with a dry clean cloth. As stated on the bag, if completing a shower or wet room, do not use shower for at least two weeks to allow the grout to fully cure.

To finish off your tiles to a professional standard, apply a bead of silicone sealant around the edges of your tiles. To find out how to apply sealant effectively, follow our how to guide here.

Learn how to clean your tiles to keep them looking brand new for longer with our cleaning guide.

Once tiled, do not turn on the underfloor heating for a minimum of 14 days. It is at this point that any underfloor heating system should be increased by approximately 5°^C per day until the maximum required working temperature is reached or as per the underfloor heating manufacturer’s recommendations. If the heating is turned on before the 14 days, there is a high chance the tiles will lift from the floor.