How to Reseal a Bath Properly, Step by Step

The silicone round a bath has one of the hardest jobs in the house. It gets soaked every day, it’s scrubbed with cleaning products, and every time someone gets in, the bath drops slightly and pulls on the joint. So it’s no surprise that bath sealant is often the first bit of a bathroom to look tired.

Here’s how to reseal a bath properly, the step that most DIY jobs skip, and when it’s worth calling in a mastic man.

Signs your bath needs resealing

You don’t need to wait for a leak. Reseal the bath if you see:

Black or pink spots in the silicone that won’t scrub off. Once mould is growing inside the sealant, cleaning won’t shift it. (We explain why in Why Is My Shower Silicone Going Black?)
Gaps, splits or edges peeling away from the tiles or the bath.
A gap that opens up when someone stands in the bath. That’s the joint failing under movement.
Water marks on the ceiling below, or a soft, swollen bath panel or floor.
Sealant that’s been put over old sealant, leaving a lumpy, layered bead.

A small crack is worth fixing straight away. Water gets behind the bath, sits there, and can damage the floor or the ceiling below long before you notice.

What you’ll need

A sharp sealant knife or scraper, and a plastic scraper for the bath edge
Silicone remover or white spirit, and clean cloths
Masking tape (optional, but it helps for a neat line)
A good-quality sanitary silicone with anti-mould protection, made for baths and showers
A sealant gun
A smoothing tool, or a wet finger with a drop of washing-up liquid

Avoid decorator’s caulk and general-purpose sealants here. They aren’t made for constant water and won’t hold up round a bath.

How to reseal a bath, step by step

Cut out all the old silicone. Every bit of it. New silicone won’t stick to old silicone, and any mould left behind will come straight back through. Take care not to scratch an acrylic bath.
Clean off the residue. Use silicone remover or white spirit to get rid of the film old sealant leaves behind, then wash and rinse.
Let it dry completely. This is where a lot of DIY reseals go wrong. Leave the joint to dry properly, ideally overnight with the window open or the fan on. Silicone put on a damp joint won’t bond.
Fill the bath with water. This is the trick most people miss. A full bath sits lower than an empty one, just like it does when someone’s in it. Seal it in that position, and the bead won’t be stretched every time the bath is used. Leave the water in until the sealant has cured.
Tape the lines (optional). Run masking tape along the tiles and the bath edge, leaving a gap the width of the bead you want.
Apply one steady bead. Cut the nozzle to suit the gap and run the silicone along the joint in one continuous movement, pushing it into the gap rather than laying it on top.
Tool it straight away. Smooth it in one pass to a neat, slightly concave finish, then peel off the tape while the silicone is still wet.
Give it time to cure. Most sanitary silicones are touch-dry quite quickly but need longer to cure fully, so follow the time on the cartridge before using the bath. Our post on how long silicone takes to dry goes into this in more detail. Then you can let the water out.

Common mistakes to avoid

Sealing over old silicone. It looks fine for a few weeks, then peels and goes black.
Rushing the drying. A joint that looks dry can still hold moisture, especially in winter.
Sealing an empty bath. The joint gets stretched the first time someone gets in, and that’s often where splits start.
Ignoring a wide gap. If the gap between the bath and the wall is wide, or the bath moves a lot, the bath may need packing or better support first, or the new seal will fail again.

DIY or call a mastic man?

Plenty of people reseal a bath themselves, and if you’re patient it’s a fair DIY job. It’s worth getting a professional in when the bath has been resealed before and keeps failing, when there’s a wide or uneven gap, when you’ve got a whole bathroom (bath, shower and basin) to do, or when you just want a crisp, straight line that looks like it came with the bathroom.

That’s our everyday work. Our bathroom and kitchen resealing service covers baths, shower trays, wet rooms, basins and worktops. We strip out every bit of old sealant, clean and dry the joint, and reseal with anti-mould sanitary silicone, using and applying products from brands such as Dow and Sika. We match the colour too, whether that’s white, clear, grey or something to suit your tiles.

We’re based in Bedford and cover the surrounding towns across Bedfordshire, as well as North London and the Hertfordshire border. Pioneer Sealants is a specialist sealant company with over 20 years in construction behind us, and we carry £5m public liability insurance. Read more about us.

Bath resealing FAQ

Can I put new silicone over old silicone?
No. It won’t bond properly and it traps mould underneath. The old bead has to come out completely.

Why should the bath be full of water when I reseal it?
A full bath sits at the same level as it does when someone’s in it. Sealing it like that stops the new bead being stretched and split the first time the bath is used.

How long before I can use the bath?
Follow the cure time on the silicone you’ve used. Leave the water in the bath until then, and keep the room ventilated.

Get your bath resealed

Send us a couple of photos of your bath and we’ll tell you what it needs. Call 01234 607 252 or WhatsApp 07757 772 880, or message us through our contact page. We’re open Monday to Friday 8:00 to 18:30 and Saturday 9:00 to 16:00.