Black mould around windows is one of the most common issues homeowners report in Wigan.
You might notice it starting as small dark spots on the window reveal or silicone seal. Over time it spreads across the corners of the frame or along the plaster.
Naturally, the first reaction is to clean it.
But if the mould keeps coming back, the real cause usually isn’t dirt or poor cleaning.
In most cases, mould around window reveals is caused by condensation forming on cold surfaces.
At Weather Wise Solutions — a family-run damp and ventilation specialist serving Wigan and Greater Manchester — we regularly diagnose mould problems linked to temperature differences around windows and airflow imbalance inside the home.
Understanding why this happens is the first step to preventing it.
❄️ Window Reveals Are Naturally Colder
Window frames and reveals are often the coldest parts of a wall.
This happens because:
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Glass loses heat faster than insulated walls
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Structural junctions create thermal bridges
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Insulation around window openings is often thinner
When warm indoor air touches these colder surfaces, moisture in the air condenses into tiny droplets.
This is the same process that causes condensation on windows.
The reveal — the plastered area surrounding the window — becomes the next coldest surface, making it a common place for mould to develop.
🌫️ Humidity Builds Up Indoors
Condensation problems don’t happen because of the window alone.
They happen when humidity inside the property rises.
Moisture is constantly produced from everyday activities such as:
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Cooking
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Showering
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Drying clothes
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Breathing overnight
If that moisture cannot escape through ventilation, humidity levels increase.
When humidity rises above roughly 65–70%, condensation becomes much more likely.
And the coldest surfaces — such as window reveals — are where it appears first.
🧱 Thermal Bridging Around Windows
Older homes in Wigan often have solid walls or older cavity construction.
Around window openings, insulation continuity can be weaker.
This creates what’s known as thermal bridging, where heat escapes more easily through structural junctions.
The result:
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Window reveals become colder than surrounding walls
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Moisture collects more easily on the surface
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Mould spores can begin to grow
Even well-maintained homes can experience this during colder months.
🚪 Why Mould Often Appears in Bedrooms
Many mould problems around windows occur in bedrooms.
This is because overnight:
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Doors are closed
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Heating levels drop
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Moisture from breathing accumulates
With limited airflow, humidity rises.
When warm air meets the colder window surfaces, condensation forms.
If this happens repeatedly, mould can begin to develop on the reveal or surrounding plaster.
🔍 How We Diagnose Window Reveal Mould in Wigan
At Weather Wise Solutions, we look beyond the visible mould.
Our investigation focuses on identifying the moisture conditions that allowed it to develop.
We assess:
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Relative humidity levels
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Surface temperatures around windows
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Ventilation performance
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Airflow pathways through the home
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Insulation continuity near window openings
Correct diagnosis ensures the problem is addressed properly rather than repeatedly cleaned.
🛠️ How to Reduce Mould Around Windows
Practical steps that often help include:
✔ Keeping trickle vents open
✔ Using extractor fans during cooking and showering
✔ Maintaining steady background heating
✔ Allowing airflow behind curtains and blinds
✔ Avoiding furniture directly against external walls
Where humidity remains high, improving ventilation can significantly reduce mould growth.
👷 Professional Standards & Independent Guidance
Weather Wise Solutions are proud members of:
🔗 Federation of Damp – https://federationofdamp.co.uk/
🔗 Damp Proofing Association – https://www.dampproofingassociation.co.uk/
Our specialists hold CPD qualifications in Dampness in Buildings and follow modern diagnostic approaches focused on identifying the root cause of moisture problems.
You can view our independent reviews here:
🔗 TrustATrader – https://www.trustatrader.com/traders/weather-wise-solutions-limited-damp-surveyor-newcastle-under-lyme
🔗 Checkatrade – https://www.checkatrade.com/trades/weatherwisesolutionslimited
If black mould keeps appearing around your windows in Wigan, the issue is usually condensation forming on colder surfaces rather than structural damp.
Controlling humidity and improving airflow can often prevent it from returning.
📍 Book a Free Survey for your home here:
https://weatherwiseuk.co.uk/pages/contact