Bathroom sealant application

Refreshing your seals every few years keeps your bathroom looking sharp and prevents costly repairs to ceilings below. While it seems like a simple task, professional application ensures a watertight bond and a smooth, aesthetic finish that lasts.

What Does the Work Involve?

• Inspection: Checking existing seals, grout integrity, and looking for signs of water ingress or loose tiles.
• Removal: Carefully stripping away old, failed silicone using specialised blades and chemical digesters to ensure a clean substrate.
• Preparation: Thoroughly cleaning and degreasing the joints with methylated spirits or professional cleaners to ensure the new bond holds.
• Mould Treatment: Applying fungicidal washes to kill any spores lurking in the gaps before sealing them in.
• Application: Laying a consistent bead of high-quality, sanitary-grade silicone around baths, showers, and basins.
• Tooling: Smoothing the sealant with professional tools to create a concave finish that encourages water run-off.

Typical Costs

Prices for bathroom re-sealing vary based on the size of the room and the condition of the existing sealant. Most tradespeople will charge a minimum call-out fee to cover travel and setup for smaller jobs.

Expect to pay more if the professional discovers significant mould that requires intensive chemical treatment or if tiles need minor re-grouting before the sealant can be applied.

How Long Does It Take?

• Single Basin: 30–45 minutes for removal and replacement.
• Standard Bath or Shower Tray: 1–2 hours depending on the difficulty of removing old material.
• Full Bathroom (Bath, Shower, Basin, Toilet): 3–5 hours for a comprehensive refresh.
• Curing Time: You must leave the sealant untouched for 24 hours before using the shower or bath.

DIY or Professional?

While sealant is available at any DIY shop, achieving a professional "bead" is harder than it looks. A poor DIY job often results in messy lines, air bubbles, and premature peeling which leads to leaks.

Hiring a professional ensures the right materials are used—such as neutral-cure silicone which adheres better to acrylic baths. There are no specific UK building regulations for applying sealant, but a professional's work will help you meet Part C (Site preparation and resistance to contaminants and moisture) by preventing damp.

Choosing the Right Tradesperson

• Look for bathroom fitters, specialist "mastic men," or experienced handymen with a portfolio of neat finishes.
• Check for "Sanitary Grade" silicone use—this contains fungicides essential for damp environments.
• Avoid anyone who suggests "over-sealing" (applying new silicone over the old).

Questions to ask:

• Do you use acetoxy or neutral-cure silicone for acrylic surfaces?
• Is the removal of all old sealant included in your quote?
• How long do you guarantee the seal against leaks?
• Do you carry insurance for accidental damage to baths or tiles?

Common Problems

• Poor Adhesion: Usually caused by failing to remove all traces of old silicone or moisture before applying the new bead.
• Black Mould Growth: Often occurs when cheap, non-sanitary sealant is used or when the room lacks adequate ventilation.
• Shrinkage: Lower-quality sealants can shrink as they cure, pulling away from the wall and creating gaps.
• Messy Finishing: Using fingers instead of proper tooling equipment often leaves a thin, uneven edge that peels easily.

Frequently Asked Questions

Can you put new sealant over the old stuff?

No. New silicone will not bond properly to old silicone, and you will likely trap mould and moisture underneath, leading to a quick failure and potential leaks.

How long should I wait before using the shower?

Most professional sealants require 24 hours to cure fully. Using the shower too early can cause the bead to deform or wash away, ruining the seal.

Why has my sealant gone black?

This is usually mould growing within the silicone. It happens when moisture sits on the surface or if the sealant’s anti-fungal properties have worn out over time.

Should the bath be full of water when sealing?

Yes. A professional will often fill the bath before sealing to account for the weight-bearing "drop." This prevents the seal from stretching and snapping the first time you take a bath.

What is the difference between silicone and caulk?

Silicone is flexible and waterproof, making it ideal for wet areas. Caulk is generally for dry areas like skirting boards as it is not as flexible and can crack when exposed to water.