How Long Does Mastic Sealant Last? (And When to Replace It)

It's one of the most common questions we get: "How long should my silicone last?" The honest answer is that it depends — but there are some clear guidelines, and some very obvious signs that tell you it's time to act.

The Short Answer

Good quality silicone sealant, applied correctly to a properly prepared surface, should last between 5 and 10 years in a domestic bathroom or kitchen. In a commercial setting with heavier use, that drops to around 3 to 5 years.

That said, plenty of silicone fails well before the five-year mark — and the reason is almost always down to how it was applied, not the product itself.

What Affects How Long Sealant Lasts?

Surface preparation

This is the biggest factor. If the surface wasn't properly cleaned, degreased and dried before the sealant went down, the bond will fail early. You'll see the sealant pulling away from the wall or tiles within a year or two — sometimes sooner.

The quality of the product used

Not all silicone is equal. Trade-grade products with antifungal additives last significantly longer than budget tubes from a DIY store. The difference in cost is small; the difference in performance is not.

Ventilation

Bathrooms with poor ventilation age sealant faster. The constant cycle of steam and condensation breaks down the surface of the silicone and encourages mould growth. If your bathroom doesn't have an extractor fan — or the fan isn't working properly — your sealant will deteriorate more quickly.

Movement

Silicone is flexible by design, but it has limits. If there's significant structural movement in the building — or if the bath or shower tray flexes under weight — the sealant joint will eventually crack. This is common in older properties and in baths that aren't properly supported underneath.

Cleaning products

Bleach-based cleaners are hard on silicone. Used regularly, they degrade the surface and accelerate discolouration. If you're cleaning your bathroom with neat bleach, you're shortening the life of your sealant.

Signs It Needs Replacing

You don't need to wait for a full failure. These are the signs that tell you a reseal is due:

Black mould that won't clean off. Surface mould can be removed with a mould spray. But once the mould has penetrated into the silicone itself, no amount of cleaning will shift it. The sealant needs to come out.

Gaps or cracks. Any break in the sealant is a water entry point. Even a small gap at the corner of a bath or shower tray can allow water to get behind the tiles and into the wall. Left long enough, this causes serious damage.

Sealant pulling away from the surface. If you can see daylight between the sealant and the tile or bath, water is already getting in. This needs sorting quickly.

Discolouration that doesn't respond to cleaning. Yellow or brown staining that persists after cleaning is a sign the silicone has absorbed contaminants. It won't improve — it needs replacing.

Bubbling or uneven texture. This usually means moisture has got behind the sealant. The bond has already failed, even if it looks intact from the outside.

Can You Reseal Over Old Sealant?

No — and this is where a lot of DIY reseals go wrong. Applying new silicone over old silicone doesn't work. The new sealant can't bond to the old one properly, so it fails quickly and looks worse than what was there before.

The old sealant has to be fully removed before anything new goes down. It's time-consuming, but it's the only way to get a result that lasts.

How Often Should You Reseal?

As a general rule:

• Bathrooms in regular use: every 5–8 years, or sooner if you see any of the warning signs above
• Showers used daily: every 3–5 years
• Kitchens: every 5–10 years depending on use
• Commercial premises: every 2–4 years

If you're not sure whether your sealant needs replacing, send us a photo via WhatsApp. We'll give you an honest assessment — no obligation.

The Cost of Leaving It Too Long

The cost of a reseal is modest. The cost of water damage behind tiles is not. Damp, rot, and mould remediation can run into hundreds or thousands of pounds depending on how long the problem has been developing.

A reseal is one of the cheapest forms of preventative maintenance you can do on a bathroom or kitchen. It's worth staying on top of it.