An expert has revealed that households are tackling black mould the wrong way
An expert has revealed the simple £1 hack for getting rid of black mould completely (Image: Getty)
Even in the height of summer, many UK bathrooms have a hidden problem that refuses to go away. Black mould around bath sealant is one of the most persistent household issues, often surviving winter, returning after cleaning and leaving households frustrated after trying everything to get rid of it.
Although experts say most people are tackling their black mould issue in completely the wrong way. While bleach sprays and scrubbing may temporarily remove visible stains, they rarely address the underlying cause, meaning the mould returns within weeks.
The experts say the real problem is not with poor cleaning but lies with the failed design of the sealant. Once the waterproof barrier around a bath or shower begins to degrade, it creates hidden pockets where moisture becomes trapped and impossible to fully remove.
That trapped moisture is what allows mould to thrive without being spotted, gradually spreading behind the sealant until it reappears on the surface again and again, no matter how often it is cleaned.
Guy Chapman, silicone seal specialist at United Silicones, says the root cause of recurring black mould is microscopic water penetration behind the sealant, something that no amount of bleach can fix.
“Standard bathroom sealant looks solid, but over time it shrinks, stiffens and pulls away from the bath edge by fractions of a millimetre,” he explains.
“Moisture gets trapped behind it, creating the perfect dark, damp environment for mould spores to grow. Once that happens, surface cleaning is pointless, the mould just keeps coming back.”
The critical failure point usually appears 6-12 months after installation, and is often completely unnoticed by the household. However, as temperatures drop and bathrooms cool faster than the rest of the house, condensation increases and accelerates the problem.
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Guy says the danger window typically begins in October, when indoor humidity rises but heating isn’t consistently on. This is when homeowners unknowingly cross the line from ‘cleanable mould’ to ‘permanent regrowth.’
Instead of ripping the sealant out from the bathroom or repeatedly reapplying bleach in hopes it will disappear, Guy recommends a simple physical barrier.
He suggests households with black mould should use a self-adhesive silicone bath strip, which costs as little as £1 from most shops.
“This works because it doesn’t rely on chemical resistance,” he says. “It physically seals over the vulnerable joint, preventing water from ever reaching the failing sealant underneath.”
Although applying the strip properly is where many households can go wrong. Guy recommends that once you finish cleaning the bathroom, the bath edge needs to be left to dry completely for at least 12 hours, as any trapped moisture will weaken the stickiness.
The strip should then be applied directly over the existing sealant, pressed firmly along the joint to form a continuous waterproof cap rather than replacing what is already there.
Guy explains: “Silicone sheet material behaves very differently from sealant compounds.It doesn’t shrink, crack or become porous over time. Once applied, it creates a stable moisture barrier that mould simply can’t penetrate.”
Unlike traditional sealant, which cures, ages and degrades, silicone strips remain flexible indefinitely, even with constant hot water exposure. The expert says the results is not just another short-term fix, but a permanent solution for an issue that never really seems to go away.
“For less than the cost of a coffee, you’re stopping mould at the structural level,” Guy says. “It’s one of the simplest preventative fixes in the home, and one of the most effective.”
