Guide to Wet Room Installation

Installing a modern wet room is a proven method for significantly increasing property value. This comprehensive guide details the technical steps involved in a professional-grade wet room installation.

A wet room is defined as a bathroom space that is entirely waterproofed (or “tanked”), featuring a level-access shower integrated seamlessly into the floor. This design delivers a clean, contemporary aesthetic. The system typically incorporates a pre-formed shower tray with an integrated drain, which is then tiled over to maintain a continuous floor level.

While wet rooms may seem like a high-cost luxury, a structured, efficient installation can be completed quickly, often taking 3–5 days for a standard size, making it a viable DIY or contractor-managed project.

The following instructions outline the critical steps for installing the specialized wet room components—the shower former (tray) and the professional-grade waterproofing (tanking) system.

Pre-Installation Checklist

• Inspection: Immediately unbox your wet room kit upon delivery. Check all components for transit damage or manufacturing defects before starting.
• Safety First: Always turn off the main water supply before commencing any plumbing or structural work.
• Professional Disclaimer: The following guidance focuses on the wet room system components (floor preparation, drainage, and waterproofing). All plumbing, electrical work, and final connections must be performed by a qualified, certified professional to ensure compliance and safety.

Required Tools and Materials

Category	Tools Required	Kit Contents (Check Your Pack)	Separately Purchased Materials
Cutting & Measuring	Circular saw, Hard point saw, Tape measure, Pencil	N/A	Wood battens, Wood screws, Plywood
Application	Electric drill, Notched trowel, Paint brushes, Silicone sealant gun, Spirit level, Standard screwdrivers	Fix-KST fixing adhesive, PRO-Seal pre-mix tape sealer, Wood floor primer, Wet room shower tray waste and trap	Silicone sealant, Tile grout, S1 flexible cement-based tile adhesive
Waterproofing	N/A	Waterproof tape, Internal wall corners	Wet room shower tray/former, Waterproof floor/tanking kit
Finishing	N/A	N/A	Tiles, Shower & valve (optional), Glass panel(s) (optional)

Estimated Completion Time: 3–5 days (Varies based on room size and curing times).

Wet Room Installation: Step-by-Step Method

The installation process is fundamentally divided into three critical phases: Structural Preparation, Drainage Integration, and Waterproofing (Tanking).

Phase 1: Sub-Floor Preparation and Positioning

1. Plan and Measure: Accurately measure the entire floor area. Sketch the layout, clearly marking the position of the wet room shower tray/former and the drain location.
2. Test Fit Components: Lay out the waterproof boards/components and the shower tray across the floor to confirm the required fit and identify any necessary cuts. Use a hard point saw for any cuts on the waterproof boards. Store them safely afterward.
3. Locate and Mark Joists: Use the existing floorboard nails or screws to mark the lines of the floor joists. Mark the centre line of the first joist outside the perimeter of the shower area. This line defines where the existing flooring will be removed.
4. Cut and Remove Flooring: Set your circular saw blade depth exactly to the thickness of the floorboards . Carefully cut along the marked lines. Remove the floorboards within the shower former area, ensuring all nails and screws are fully extracted.
5. Secure Remaining Floor: Verify that the remaining perimeter floorboards are absolutely flat, level, and securely fastened to the joists.

Phase 2: Drainage and Structural Support

6. Install Drainage Pipe: Apply a solvent weld adhesive inside the drain connector. Twist the shower drain base onto the connector. Repeat the process to secure the other end of the connector to the main waste pipe.
7. Water Test: Once the solvent weld is fully cured, pour water down the drain to confirm proper flow and check for any leaks at the connections.
8. Install Joist Support Battens: All exposed joists must be supported to accommodate the new sub-floor. Cut timber battens. Screw these battens to the inside face of the joists, ensuring the top of the batten is positioned below the top of the main joists.
9. Fit Plywood Sub-floor: Cut plywood to fit precisely between the joists, resting on the newly installed support battens.
10. Cut Drain Hole: Measure and mark the exact position of the shower drain base onto the plywood. Use a jigsaw to carefully cut a hole so the drain base and connector are accessible and fully exposed through the new floor.
11. Final Leveling: Use any discarded floorboard pieces to fill any remaining small gaps between the new plywood and the edge of the shower tray area to ensure a flat sub-floor plane.

Phase 3: Installing the Shower Tray and Waterproofing

12. Primer Application: Position the wet room shower tray to verify alignment with the drain. Remove it and set it aside. Paint the entire exposed floor area (including the new plywood sub-floor) with the wood floor primer. Allow at least 30 minutes for the primer to dry.
13. Bed the Shower Tray: Spread the Fix-KST adhesive evenly over the shower tray area. Use the notched trowel to create an even, suitable bed of adhesive. Carefully place the wet room shower tray into position, pressing firmly into the adhesive. Use a spirit level to confirm the tray is level in all directions.
14. Secure Drain Components: Place the internal drain bowl and lock the internal dome into the drain base.
15. Drain Sealing: Apply a thin bead of silicone sealant around the top of the drain base and the outer perimeter of the shower tray. Secure the drain top with screws and allow the silicone to fully cure.
16. Affix Waterproof Boards: Spread Fix-KST adhesive over the rest of the floor area and use the notched trowel to prepare the surface. Place the first waterproof board into position, bedding it down onto the adhesive. Repeat for all remaining boards. Allow the boards and adhesive to set for approximately 3 – 4 hours.
17. Reinforce Joints and Corners (Tanking):
    • Fixing Plates: Screw the provided metal fixing plates over all board joints at intervals, centring the hole over the join line.
    • Internal Corners: Place the waterproof internal corners into position and mark their outlines. Apply a thin layer of Pro-SEAL pre-mix tape sealer with a paintbrush, slightly overlapping the marks. Press the internal corner firmly into the sealer, then apply a second thin layer over the top.
    • Tape Joints: Apply a thin layer of Pro-SEAL tape sealer, approximately wide, along all wall/floor junctions and all remaining board joints/fixing plates. Firmly embed the waterproof tape strips into the sealer, then apply a final thin layer of Pro-SEAL over the tape.

Phase 4: Tiling and Finishing

18. Tiling Guides: Place the shower drain top upside down and mark around its edge. Set the drain top aside and mark straight lines from the four corners of this square to the corresponding corners of the wet room shower tray. These lines act as guides for maintaining the necessary fall (slope) in your tiling.
19. Apply Tiles: Tile the shower tray area and the rest of the floor using an S1 flexible cement-based tile adhesive.
    • Note on Slope: If your chosen tiles are larger, you must cut them along the pre-marked slope lines to ensure the correct gradient is maintained toward the drain.
20. Fit Drain Top: Measure the distance from the top of the finished tile to the top of the shower drain base. Mark and cut the plastic shower drain top to this exact height using a hard point saw. Refit the O-ring onto the lowest remaining indent.
21. Grout and Seal: Gently ease the drain top into position. Fill the small gap between the drain top and the surrounding tiles with the same grout used for the main floor. Place the decorative shower drain finishing grate into position.
22. Cure Time: Allow the entire installation to dry for a minimum of 24 hours before using the shower.

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Congratulations! You have successfully completed the fitting of your new wet room shower tray, waste, and waterproof flooring system.

Important Professional Guidance

While DIY offers cost savings, the structural and waterproofing phases are highly technical. It is strongly recommended that you engage a qualified professional for the complete plumbing, electrical, and final installation of your shower unit and accessories. The instructions provided serve as a guide for fitting the tanking kit and floor former but do not replace the expertise of a certified tradesperson for the plumbing and safety-critical connections.

Explore our extensive selection of wet room products, including tanking kits, glass screens, tiles, and designer shower systems, to complete your project.