As UK homes head into the colder, damper months, bathrooms quietly become one of the biggest mould danger zones. With windows staying shut and humidity levels rising, black mould around bath sealant is set to surge, and experts warn most people are tackling it the wrong way.
Guy Chapman, Silicone Seal Specialist at United Silicones, says the root cause of recurring black mould is microscopic water penetration behind the sealant, and a £1 item can fix it.
“Standard bathroom sealant looks solid, but over time it shrinks, stiffens and pulls away from the bath edge by fractions of a millimetre,” he said.
“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.”
According to the expert, the critical failure point usually appears 6-12 months after installation, often unnoticed.
Mr Chapman 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 out sealant or repeatedly reapplying chemicals, the expert recommends a simple physical barrier: a self-adhesive silicone bath strip, costing as little as £1.
“This works because it doesn’t rely on chemical resistance,” he said. “It physically seals over the vulnerable joint, preventing water from ever reaching the failing sealant underneath.”
How to apply the strip properly:
1. Dry completely
After cleaning, leave the bath edge dry for at least 12 hours. Any trapped moisture will compromise adhesion.
2. Bridge, don’t replace
Apply the silicone strip directly over the existing sealant, pressing firmly along the joint to create a continuous waterproof cap.
Mr Chapman added: “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. This means the result is a permanent solution rather than another cleaning cycle.
“For less than the cost of a coffee, you’re stopping mould at the structural level,” he said.
“It’s one of the simplest preventative fixes in the home, and one of the most effective.”
