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Step-by-step solution

Sanitary sealing (baths, basins, showers and kitchen tops)

Silicone joints where tiles meet baths, shower trays, basins, WCs and kitchen worktops. Choose a mildew-resistant sealant that suits the surface, and reseal before water gets behind the tiles.

  • 6 steps
  • 2 products
  • 5 answers
Bath against a tiled wall with an orange silicone bead where the bath rim meets the tiles, and a shower running

Get this solution priced Proposal brief ↓

You need this when…

  • Black mould in the silicone around the bath or shower
  • Sealant peeling away from the tiles
  • Water running behind the vanity or kitchen worktop
  • Damp ceiling below a bathroom

The work, step by step

General guidance based on the manufacturer data sheets. Site conditions differ: confirm the system with MCT before you start. Where we do not name a product, ask us and we will confirm the right one.

  1. Step 1: Cut out the old sealant and clean

    The surface must be sound, clean and dry, free of dirt, oil, grease, old sealant and poorly bonded paint (Sika Sanisil p.3). Let the area dry fully before resealing.

  2. Step 2: Choose the sealant for the surface

    Sika Sanisil is a mildew-resistant silicone for sanitary joints and domestic kitchens, with very good adhesion to non-porous surfaces (Sika Sanisil p.1). Do not use it on concrete, plaster, render or brick, or on porous stone, marble or granite (Sika Sanisil p.2). Sikasil-715 WS is a neutral-cure, antifungal silicone listed for wet-area joints in bathrooms, toilets and kitchens and around sanitaryware (Sikasil-715 WS p.1).

    Sika Sanisil Sika Request a quotation

    Sanitary or other sealing applications where mildew and fungus resistance is required Domestic kitchens For interior and exterior use (TDS p.1)

    Temperature stated in TDS
    +5 °C min. / +40 °C max (TDS p.2)
    Pack
    300 ml cartridge: 12 cartridges per box

  3. Step 3: Pre-treat and mask

    For demanding joints, lightly roughen glazed tiles and aluminium, then pre-treat them with Sika Aktivator-205. Clean glass with isopropanol (Sika Sanisil p.3). Mask the edges for neat lines (Sika Sanisil p.3).

  4. Step 4: Back up wide joints

    For joints 10–20 mm wide, a sealant depth of 10 mm is recommended. Use a closed-cell polyethylene backer rod (Sika Sanisil p.2).

  5. Step 5: Apply and tool

    Fill the joint in full contact with both sides, with no trapped air. Tool it firmly. Water can be used as a tooling aid, but not solvent products. Remove the masking within the skin time of about 25 minutes (Sika Sanisil p.2, p.3).

  6. Step 6: Let it cure before use

    Sika Sanisil cures about 3 mm per 24 hours at +23 °C. It needs air moisture to cure, so it is not for fully confined spaces (Sika Sanisil p.2).

Proposal brief

Sanitary sealing (baths, basins, showers and kitchen tops): scope and system

A starting point for a site proposal. Quantities, prices and the final specification follow a site visit or photos.

Scope of work

  1. Removal of old sealant at x baths, basins, showers and worktops
  2. Cleaning, drying and pre-treatment
  3. Resealing with mildew-resistant silicone
  4. Curing time advice before use

System build-up

StepProductPackSource
2. Choose the sealant for the surfaceSika Sanisil300 ml cartridge: 12 cartridges per boxTDS p.1 · May 2021, Version 03.01
2. Choose the sealant for the surfaceSikasil-715 WS300 ml cartridge, 12 cartridges per boxTDS p.1 · May 2025, Version 03.01

What we need from you

  • Number of fittings and approximate joint length
  • Surfaces involved (glazed tile, acrylic bath, stone top, mirror)
  • Photos of the current joints
  • Is there damp or a leak below?

Site conditions

  • Fittings out of use until the sealant has cured (Sika Sanisil p.2)
  • Dry joints at the time of sealing (Sika Sanisil p.3)

Not included

  • Plumbing leaks and fitting replacement
  • Regrouting or waterproofing behind the tiles, which is quoted separately

Questions customers ask

Can I seal around a mirror with it?

Not with Sika Sanisil. The acetic acid released during curing can corrode mirror silver (Sika Sanisil p.2). Sikasil-715 WS is a neutral-cure silicone (Sikasil-715 WS p.1).

How long before I can use the shower?

Sika Sanisil cures about 3 mm per 24 hours at +23 °C, so deeper joints need longer (Sika Sanisil p.2).

Can I paint the silicone?

No. Sika Sanisil cannot be over-painted (Sika Sanisil p.2).

Which sealant for a marble vanity top?

Sika Sanisil is not recommended on marble or granite, because staining may occur (Sika Sanisil p.2). Sikasil-715 WS lists natural stone after checking with Sika (Sikasil-715 WS p.1).

Why does the silicone go black?

Mould grows on soap and moisture. Sika Sanisil has long-term fungus and mildew resistance (Sika Sanisil p.1), and Sikasil-715 WS is tested as antifungal (Sikasil-715 WS p.1). Reseal over clean, dry surfaces.

Steps and product facts are taken from the manufacturer data sheets (page cited). Products are named only where the data sheet confirms the use; quantities follow a site visit or photos. General guidance: check the data sheet or ask us before you start.