Bathroom Subfloor for Stone Resin Shower Tray and Tiles

When installing a stone resin shower tray and tiles, it is crucial to have a solid, properly-supported base to ensure stability and longevity. Here are the recommended steps for preparing your bathroom subfloor for this purpose: 1. Remove old flooring: Carefully remove the existing floorboards to expose the joists underneath. 2. Check joist integrity: Inspect the joists for any signs of rot, damage, or unevenness. If necessary, repair or replace them to ensure a stable subfloor. 3. Add noggins: Install noggins between the joists to provide additional support and minimize any flexing in the floor. Noggins should be securely fixed and spaced evenly across the floor to distribute weight evenly. 4. Install a subfloor: Lay 3/4″ pressure-treated plywood directly onto the joists and noggins, making sure to stagger the joints for added strength. Secure the plywood with screws, making sure they are flush with the plywood surface. 5. Waterproofing membrane (optional): Depending on the specific requirements of the stone resin shower tray and the tiles, you may need to add a waterproofing membrane on top of the plywood. Consult the manufacturer's guidelines for their recommendations. 6. Install Hardibacker or cement backer board: Lay a suitable cement backer board (like Hardibacker) on top of the plywood or waterproofing membrane, and secure it with screws specified for this purpose. The cement backer board provides an ideal surface for tile adhesion and helps protect the plywood from moisture damage. 7. Tape and seal joints and screws: Apply alkali-resistant fiberglass mesh tape over the joints and screw holes, followed by a thin layer of thinset mortar to create a smooth, continuous surface. 8. Allow the subfloor to dry and cure: Follow the manufacturer's guidelines for curing times and recommended practices before proceeding with the installation of the shower tray and tiles. With a properly-prepared subfloor in place, you can install your stone resin shower tray and tiles, ensuring a stable and long-lasting bathroom setup.

Hi. You can use the 3/4″ (18mm) ply under the shower tray as it is fairly rigid stone but on the rest of the bathroom go with 25mm ply under tiles. We usually replace the whole floor with 25mm when doing complete refurb. Hope that helps.

If you are tiling the floor you will have to overlay the boards with plywood or backer sheets regardless. These wouldn’t have to be 18mm thick but even 6 mm (plus tiles) may not work well at the doorway. So you could remove boards and replace with ply but you will only save about 6 mm height and a lot of work and expense.