Mould can be more than just an unpleasant patch on your wall, it can harm your health, damage your property, and leave you wondering what’s going on beneath the surface of your home. According to the UK Health Security Agency, there are around 2 million people living in homes with significant damp and/or mould in the UK. Whether it’s creeping across bathroom tiles or reappearing in the corners of a bedroom, mould is a problem no homeowner wants to deal with. But what if you’ve cleaned it, repainted, opened windows, and it still comes back?
In this guide, we’ll explain how mould starts, how to stop it from spreading, and why in some cases, a hidden water leak might be the root of the problem. If you live in South-East England, you’ll also learn why local homes are particularly prone to mould, and what you can do about it.
Why Does Mould Occur in Homes?
Mould needs three things to grow: moisture, warmth, and poor ventilation. That’s why it often shows up in bathrooms, kitchens, or behind furniture where air doesn’t circulate well.
In the UK, our older housing stock and damp climate don’t help. Many homes have less insulation, single glazing, or rooms that just don’t breathe well. Everyday things like showering, cooking, and drying clothes indoors can raise humidity, and if that moisture doesn’t escape, mould starts to form.
One of the most overlooked causes? Water leaks – especially the kind you can’t see. A slow leak behind a wall, under flooring, or inside a ceiling can create perfect mould-growing conditions without you realising it’s even there.
How Mould Affects Your Health
According to the NHS, exposure to damp and mould can trigger a range of health issues. For some, it’s mild – coughing, sneezing, or irritated eyes. But for people with asthma, poor immune systems, or long-term conditions, mould can make symptoms worse or lead to more serious problems.
Children and elderly people are especially at risk, which is why mould shouldn’t just be cleaned, it should be prevented. And the best way to do that is to tackle the moisture at its source.
How to Prevent Mould in Your House
Most homeowners can reduce or eliminate mould by making small changes to airflow, moisture control, and maintenance.
1. Let Your Home Breathe
Ventilation is key.
- Open windows for at least 10–15 minutes a day
- Use extractor fans in bathrooms and kitchens
- Leave internal doors open where possible
- Avoid pushing furniture right up against cold external walls
Fresh air helps moisture escape and makes it harder for mould to settle in.
2. Keep an Eye on Humidity
Ideally, indoor humidity should be between 40–60%. You can buy a cheap digital hygrometer online to monitor and measure it.
If it’s regularly higher, use a dehumidifier in affected areas – especially in winter. Dry clothes outside if possible, or in well-ventilated rooms with a window open.
3. Deal With Condensation Early
Condensation often appears on windows and walls when warm air hits a cold surface. Wipe it down quickly and try not to ignore repeated patterns – it’s usually a sign that moisture is hanging around longer than it should.
4. Fix Any Obvious Leaks or Damp Patches
Dripping taps, leaking washing machine pipes, or damp patches on ceilings should be fixed promptly. The longer water sits, the higher the likelihood is of mould growing.
5. Watch for Signs of Hidden Moisture
Sometimes there’s no visible leak, just a persistent damp smell or mould that keeps reappearing in the same place.
- Musty odours
- Cold, damp-feeling walls
- Peeling paint or wallpaper
- Floors that feel warped or soft underfoot
These can all point to a hidden leak, especially under tiled bathrooms or behind fitted kitchens.
6. Use Mould-Resistant Products
If you’re decorating, use anti-mould paint or sealants in high-risk areas. In bathrooms or kitchens, consider moisture-resistant plasterboard or better ventilation systems when upgrading.
Still Dealing with Mould No Matter What You Try?
If you’ve followed all the advice: ventilated, dehumidified, cleaned, painted, and mould still returns, there’s a good chance there’s an underlying moisture issue, like a slow leak.
And not all leaks show themselves with puddles or stains. A pipe could be dripping inside a wall, or beneath your bathroom tiles, silently feeding damp into the structure of your home.
Why Hidden Leaks Cause Long-Term Mould
Hidden leaks are one of the most common (and frustrating) causes of repeat mould problems. The leak might be tiny, but over weeks or months, it creates a moist environment that’s perfect for mould to thrive.
And the tricky part? It’s often invisible. You might only notice mould, not the leak itself.
That’s where non-invasive leak detection comes in. With thermal imaging, acoustic listening devices, and tracer gases, professionals can pinpoint a leak without having to take up your floors or drill into your walls.
This kind of advanced detection is especially helpful in older or renovated homes across South-East England, where plumbing can be complex and leaks harder to trace.
When Should You Call a Leak Detection Expert?
If you notice any of the following, it’s time to speak to someone who can investigate further:
- Mould coming back after cleaning or decorating
- A damp smell with no clear source
- Sudden increases in water bills
- Cold, clammy walls or floors
- Damp patches that change size or shape
Catching a leak early can prevent major repairs and finally put an end to mould that keeps coming back.
Need Help Finding the Source of Mould?
If you suspect hidden leaks are contributing to mould in your home, our friendly team at Harmuns can help. Our engineers are gas-safe heating engineers by background and are WIAPS approved. Based in the South-East England, we use non-invasive leak detection methods to locate even the hardest-to-find leaks so you can stop mould at the source and keep your home healthy and dry.
Frequently Asked Questions (FAQ)
What is the best way to prevent mould in a house?
Keep your home well-ventilated, monitor humidity levels, and dry out any condensation or leaks quickly. Good airflow and moisture control are key.
Can mould be caused by hidden water leaks?
Yes – many long-term mould issues are caused by slow leaks behind walls or under floors. These leaks create damp conditions that allow mould to grow unnoticed.
How do I tell if I have a leak inside my walls?
Look for signs like persistent mould, musty smells, soft flooring, or unexplained damp areas. A professional can confirm using non-invasive tools.
What health problems can mould cause?
According to the NHS, mould can cause or worsen breathing issues, asthma, allergies, and infections, especially in children, elderly people, or those with existing health conditions.
Who do I call if I can’t find the source of mould?
A specialist leak detection company like Harmuns can help identify and fix hidden leaks that may be causing repeat mould issues.