How to Seal Shower Screen

A leaking shower screen is almost always a sealant failure rather than a structural problem. The silicone bead along the base and sides of the screen degrades over time, often within a few years in a heavily used shower, allowing water to creep behind tiles or into the shower tray edge. Resealing takes under two hours of active work and costs less than £20 in materials, yet most plumbers charge £80–£150 to do it for you.

The single biggest cause of failure in DIY resealing is poor preparation: applying new silicone over old leaves a bond that lasts months, not years. Follow the steps below and your new seal should outlast the original.

Tools and Materials

On silicone choice: Use a sanitary-grade, anti-mould silicone rated for permanently wet areas. These contain biocides that slow mould growth significantly.¹ Avoid general-purpose or decorator’s sealants, they are not formulated for continuous water exposure and will crack or blacken quickly. Sealants for these joints are covered by BS EN 15651-3, the British Standard for sealants for sanitary joints in bathrooms, showers and kitchens.²

Step-by-Step Instructions

1. Remove All Old Silicone

This is the most important step. New silicone will not bond reliably to old silicone.

• Score along both edges of the old bead with a Stanley knife, keeping the blade flat to avoid gouging tiles or the shower tray.
• Grip the bead and pull it away in one strip where possible. Stubborn sections may need repeated scoring.
• Apply silicone remover gel to any remaining residue, leave for 30–60 minutes, then scrape away with a plastic tool.
• Repeat until the substrate is clean: tile, glass, and shower tray surfaces should be free of any visible silicone.

Pro tip: Work in good light, a torch held at a shallow angle reveals thin silicone traces that look clean to the naked eye.

2. Clean and Degrease

Any moisture, soap residue, or grease will prevent a good bond.³

• Rinse the joint area and allow to dry completely, ideally leave overnight, or use a hairdryer on a low setting for 10–15 minutes.
• Wipe all surfaces with isopropyl alcohol (IPA). Allow to evaporate for 5–10 minutes. Do not use washing-up liquid or bathroom cleaner at this stage, they leave a film.

3. Apply Masking Tape (Optional but Recommended)

• Run two strips of low-tack masking tape parallel to the joint, each set back 3–4 mm from the edge. This creates a channel for the sealant and gives a clean, straight finish.
• Press the tape edges down firmly to prevent silicone bleeding underneath.

4. Cut the Nozzle and Load the Gun

• Cut the nozzle at a 45-degree angle, leaving an opening of approximately 4–5 mm. Too large an opening deposits excess silicone; too small makes the bead difficult to control.
• Load the cartridge into the gun. Squeeze the trigger gently until silicone reaches the tip.

5. Apply the Bead

• Hold the gun at 45 degrees to the joint. Move steadily and consistently along the full length of the joint in one continuous pass where possible.
• Apply moderate, even trigger pressure. A common mistake is stopping mid-run and restarting, which leaves a visible join and a potential weak point.
• Aim to slightly overfill the joint, you will smooth it down in the next step.

6. Smooth the Bead

• Dip a finger in the bowl of soapy water, this prevents silicone sticking to your skin.
• Draw your wetted finger along the bead in one smooth, consistent motion, pressing it firmly into the joint. The silicone should form a slightly concave profile, which sheds water away from the joint rather than collecting it.
• If using masking tape, remove it immediately after smoothing, before the silicone skins over. Pull the tape back at 45 degrees to the joint.
• If you need to correct a section, re-wet your finger and work quickly: silicone starts to skin within minutes, and Everbuild, for example, says to tool its Forever White sanitary silicone within 15 minutes of applying.¹

7. Allow to Cure

• Do not use the shower for a minimum of 24 hours. Sanitary silicones typically cure at about 2–3 mm per 24 hours, so allow 48 hours for a thick bead.¹
• Keep the bathroom ventilated during curing: silicone cures by reacting with moisture in the air, and its skinning time and curing speed vary with temperature and humidity.³
• Avoid touching the bead during curing.

Common Mistakes

Applying over old silicone. The new bead will peel away within weeks. There are no shortcuts to complete removal.

Using the shower too soon. Water on the bead before it has cured can disturb it and weaken the seal, inviting early leaks and mould.

Using the wrong product. Kitchen sealants, external sealants, and decorator’s acrylics are not designed for permanent submersion. Always check the label for “sanitary” and “anti-mould.”

Applying to damp or cold surfaces. Sanitary silicone needs a clean, dry surface, and typical products are rated for application only between +5 °C and +35 °C.³ In winter, warm the room before working.

Leaving gaps at the ends of the run. Water finds any gap. Ensure the bead runs fully into corners and terminates neatly at any edge junctions.

Dealing With Mould Behind Old Silicone

When you remove the old bead and find black mould on the tile or tray surface beneath, treat it before resealing:

• Apply a bleach-based mould spray, leave for 10–15 minutes, then scrub with an old toothbrush.
• Rinse thoroughly and allow to dry completely before proceeding.
• If mould penetrates the grout or tile adhesive, the tiles may need to be removed and re-laid, resealing over contaminated substrate is a temporary fix only.

When to Call a Professional

DIY resealing is appropriate for surface-level sealant replacement where the screen, tray, and tiles are all structurally sound. Get a professional involved if:

• Water has been leaking behind tiles for an extended period, tapping tiles reveals hollow spots indicating failed adhesive, and affected tiles should be re-fixed before resealing.
• The shower tray is cracked, flexing, or not level, no amount of silicone will seal a tray that moves under load.
• The shower screen frame is corroded or the screen itself is loose in its fixings.
• You are uncomfortable working on large walk-in screens or frameless glass panels where incorrect handling could cause breakage.

A bathroom tiler or plumber will typically charge £80–£150 for a reseal job, or up to £400–£600 if tile repairs are also required.