Mould on bath and shower silicone: how to deal with it

Mould on silicone around a bath or shower usually calls for two checks: remove the visible mould appropriately, then find why that edge stays damp. Bathroom condensation may be involved, but a broken seal can also let water escape where it should not. If the seal is damaged, cleaning its surface will not repair it. Look at the whole area before deciding what needs doing.

Is it condensation or a failed seal?

Showering adds moisture to indoor air. If that moisture cannot escape, it can condense on colder surfaces and, over time, lead to mould. A mouldy line at the bath edge may therefore be part of a wider condensation problem. Notice whether there is water on nearby tiles or windows and whether other bathroom surfaces are becoming mouldy as well.

Check the seal itself too. RICS identifies broken mastic seals around showers as a possible route for internal water leaks and advises replacing broken seals around showers, baths and sinks. A gap or damaged section deserves attention even if the visible mould is small. If nearby surfaces are damp beyond the splash area, the source of the water needs investigating rather than assuming it is all ordinary bathroom steam.

It helps to describe exactly what you see: mould sitting on a sound-looking edge, an obvious break in the seal, water collecting on adjacent surfaces, or damp appearing farther away. Those observations do not prove the cause, but they lead to more useful next steps than treating every dark mark as a cleaning issue.

Clean a small patch, then let it dry

Government guidance says mould on hard surfaces can be removed with an appropriate cleaning product and the surface should be left to dry completely. It recommends mould and mildew products in preference to bleach. Follow the product instructions and avoid treating a large affected area as a routine wipe-down; government guidance says larger areas of mould should be dealt with by qualified professionals.

Cleaning answers the visible part of the problem. It does not tell you whether a seal is still keeping water where it belongs or whether moist air is lingering in the bathroom. If the mould returns in the same place, revisit those questions instead of simply repeating the clean. Government guidance is clear that removing surface mould without addressing the underlying cause will not stop it reappearing.

Keep bathroom moisture moving

Use the bathroom's ventilation when showering and check whether it is working effectively. Government guidance points to extractor fans in bathrooms and opening windows periodically as ways to reduce condensation. If the room remains wet and condensation gathers after use, the ventilation may need attention. A cleaning routine cannot make up for moist air that has nowhere to go.

Wipe condensation from tiled surfaces and windows with a dry cloth or sponge. This can help prevent mould growth on those cooler surfaces. Keep an eye on whether moisture is limited to the shower edge or shows up elsewhere. A bathroom with repeated damp patches may have more than one water source, so focus on the pattern rather than blaming a single habit.

A Yorkshire or Lancashire bathroom behind the seal

In a Yorkshire or Lancashire terrace, the bathroom may sit against an external wall. If a patch near the bath seems to extend beyond the silicone line, it is sensible to look beyond the joint. Indoor condensation can gather on a cold wall, while a broken shower seal can allow water to travel elsewhere. The appearance of mould alone does not show which route is at work.

Do not let the local character of an older house become an explanation by itself. Look for a damaged joint, note where the damp begins and consider whether the room clears moisture after bathing. If the area stays damp after a broken seal has been replaced, that is useful evidence that the investigation should continue.

When the problem needs more investigation

If a seal is broken, have it replaced as part of addressing the water route. If mould is extensive, keeps returning, or damp appears beyond the bath or shower, ask an independent, suitably qualified surveyor with relevant damp experience to find the cause. RICS notes that moisture can travel from a leaking shower under floor coverings and affect other areas, so a wider pattern deserves proper attention.

If you rent, tell your landlord or managing agent about mould that concerns you and mention any damaged seal or damp outside the shower area. The useful outcome is an explanation of where the water comes from, action on any defect and a check that the mould does not return. That is more reliable than judging success by whether the silicone looks clean immediately after treatment.

This page gives general information, not legal or medical advice. For your own situation, use the organisations listed under "Where this comes from" at the foot of the page.