How do I seal where bathroom wall panelling meets a bath or shower tray?

PVC and composite shower panelling solves the grout problem and introduces a different one. The panel is a sheet with a hollow or foam core and a decorative face, and if water reaches that core through a cut edge it travels inside the panel where nothing can dry it. The bottom edge, sitting right where the water runs, is the most exposed cut edge in the installation, and how it is detailed decides whether the panelling lasts.

What you'll need

• The manufacturer's recommended sealant or adhesive for the panel system
• Sanitary-grade silicone
• An end profile or bottom trim, if the system has one
• A fine-toothed saw for trimming the panel
• Low-tack masking tape
• A silicone finishing tool

Step by step

1. Use the panel system's own trims and sealant.Panelling is a system: the panels, the internal and external corner profiles, the end caps and a specified sealant that bonds to that plastic. Silicone that bonds beautifully to tile may not bond to a particular PVC. Use what the manufacturer specifies for the panel-to-panel joints, and use a good sanitary silicone at the visible bath joint.
2. Set the panel to sit above the rim, not on it.The panel's bottom edge should finish a few millimetres above the bath or tray rim, leaving a gap for a sealant joint. A panel resting hard on the rim has no joint to accommodate movement, and the bath moving under load will lift or split it.
3. Trim the panel accurately and cleanly.Cut the bottom edge square with a fine-toothed saw and a straight edge. A ragged edge cannot be sealed and it will not sit at a consistent height. Cut with the decorative face up if using a hand saw, face down for a circular saw, to avoid chipping the face.
4. Seal the cut edge itself.This is the step that is routinely skipped. Run sealant into the exposed core along the cut bottom edge before the panel goes up, or fit the system's bottom trim which encapsulates it. Water reaching an open core travels inside the panel and cannot dry.
5. Bed the panel as you fit it.Apply the specified adhesive or sealant to the wall in vertical beads and press the panel home, then run a bead behind the bottom edge as well so there is no open path behind the panel to the wall. The idea is that water can never get behind the panel in the first place.
6. Fit the bottom trim if the system has one.Some panelling systems supply a bottom or 'end' profile designed to sit on the bath rim with the panel slotted into it. Where one exists, use it — it encapsulates the cut edge and gives a defined joint to seal. Bed it in sealant as it goes on.
7. Load the bath or tray before the final bead.Fill the bath, or stand in the tray, so the joint is at its widest when the sealant cures. It is then compressed in normal use rather than stretched.
8. Mask and run the visible bead in one pass.Tape both sides — the panel face and the bath rim — leaving the width you want. Cut the nozzle at 45 degrees to slightly under the joint width and run one continuous bead. Tool it concave once with a finishing tool, then pull the tape immediately while the silicone is wet.
9. Do the corners and the ends properly too.The vertical corner between two panels, and the ends where the panelling stops, are the other places water gets behind. Corner profiles bedded in sealant, end caps on any exposed vertical edge, and a bead where the panelling meets anything else.
10. Leave it to cure fully.Twenty-four hours before any water, and keep the bath full or the tray weighted for as long as you reasonably can while it skins. Then drain slowly.

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