Tiling onto floating floors
Floating floors is a term used for a floor that is not attached to a rigid substrate. Generally this will be a tongued and grooved wooden board above an acoustic or insulation material. They are used to improve floor insulation and/or to reduce noise. Normal wooden floors flex when loaded but this movement is even greater on a floating floor as the boards are not supported by joists.
1.1 As a floating floor is not supported by joists, any applied load creates significant movement over a big area. This can be felt as bounce in the floor when it is walked across. As the applied load increases so does the severity of movement.
1.2 The edges of a floating floor are even more susceptible to exaggerated movement as they are not supported and any applied load is spread over a smaller area.
If the adhesive used to fix the tiles is not flexible or thick enough to absorb the amount of movement, the tiles will either delaminate or crack. Large tiles will exacerbate the deflection across each tile's width.
2. Unsupported joints
When a floating floor is overboarded to add rigidity, the extra board has to be securely attached to the original boards. If nails are used, constant movement of the floor can loosen them, press on the underside of the tile and cause cracks. If the screws/nails used are too long they can bottom out on a rigid surface underneath and create a column, over which tiles will crack.
Overboarded with plywood or tile backer-board
Although small tiles can be fixed onto small areas of tongued and grooved floating floors using weberset plus & weber AD250, a more secure solution is to fix a second board over the existing timber. This increases the rigidity and prevents localised movement. If a water-resistant tile backer-board is used to overboard, it will virtually eliminate any moisture related movement.
Stage 1: Preparation
Verify that the extra height from the over-boarding can be accommodated and that the floor is capable of supporting the expected load. All tongued and grooved boards should be glued together securely and wedged around the edges until dry.
Stage 2: Fix the over-boarding
Use WBP grade plywood at least 15mm thick. Prime the back and edges of the plywood with weber PR360. Lay the boards so that the joints do not coincide with joints in the existing timber and leave slight gaps between boards to allow for expansion. Screw the boards at 200 to 300mm. Leave a movement joint around the perimeter for expansion.
Stage 3: Fixing the tiles
Fix the tiles into at least a 5mm thick solid bed of weberset plus & weber AD250. Leave joints at least 3mm wide for grouting and make provision for movement.
Leave the adhesive to set and then grout the tiles with weberjoint wide flex or weberjoint pro. Use weberjoint silicone sealant to fill the perimeter movement joints.
Solution with the following Weber products
Styrene acrylate dispersion for use with tile adhesives, levelling compounds and webersys protect
A standard-setting non-slip tile adhesive for low-porosity tiles and substrates
An acrylic primer and admixture for use with cement-based adhesives
A wide-joint, mould-resistant, flexible tile grout for interior and exterior use
A water-repellent, mould-resistant, flexible tile grout for interior and exterior use
Acetoxy curing silicone sealant that cures to form a tough, flexible, water tight seal – available in clear, white and a range of colours