As a Bolton estate agent we know the importance of dealing with mould and condensation early.
Damp patches, black spots on the wall, a musty smell… it’s enough to make any homeowner or tenant worry. But before jumping to conclusions, it’s important to ask: is it mould or condensation?
In the UK — where wet, cold winters and older housing stock are common — these issues frequently arise. Yet while mould and condensation are related, they’re not the same thing. And identifying the cause is key to fixing the problem properly.
In this blog, we’ll help you:
• Spot the difference between mould and condensation
• Understand what causes each
• Learn how to prevent and treat both issues
• Know when to call in the professionals
🌫️ What is Condensation?
Condensation happens when warm, moist air hits a cold surface — like a window, wall, or mirror — and turns into water droplets. This is a common and natural process, especially in winter, when indoor air is warm but exterior walls and windows are cold.
Common signs of condensation:
• Water droplets on windows in the morning
• Damp patches on cold walls or corners
• Peeling wallpaper or bubbling paint
• A general feeling of dampness in the air
Condensation is most noticeable in bathrooms, kitchens, and bedrooms, especially where ventilation is poor.
🦠 What is Mould?
Mould is a type of fungus that thrives in damp, humid conditions. It often appears when condensation is left untreated over time. But mould can also be a symptom of structural damp (like rising damp or leaks), not just excess moisture in the air.
Common signs of mould:
• Black, green, or white fuzzy spots on walls, ceilings, tiles, or around windows
• A strong, musty smell
• Spores forming on furniture, curtains, or clothes
• Persistent stains that return even after cleaning
Mould is more than just unpleasant — it can also pose health risks, especially for those with asthma, allergies, or weakened immune systems.
Often, condensation is the cause, and mould is the result — but not always.
If you see black spots forming in damp corners, especially where airflow is poor (behind furniture, in window recesses), there’s a good chance mould is forming because of condensation.
🛠️ What Causes Condensation and Mould in UK Homes?
Main causes:
• Poor ventilation (no extractor fans or blocked vents)
• Cold surfaces (single-glazed windows or uninsulated walls)
• High humidity (cooking, bathing, drying clothes indoors)
• Lack of heating (or inconsistent heating)
UK homes, particularly older properties or flats with poor insulation, are especially prone to these conditions — especially in the winter months.
✅ How to Prevent Condensation in Your Home
1. Ventilate Daily
o Open windows each morning for 10–15 minutes
o Use extractor fans in kitchens and bathrooms
o Avoid blocking air vents or trickle vents
2. Control Indoor Humidity
o Use lids when cooking and open windows after showers
o Dry clothes outside if possible or use a vented tumble dryer
o Consider using a dehumidifier in trouble spots
3. Maintain Steady Heating
o Keep your home at a consistent temperature
o Avoid letting rooms get too cold (below 15°C)
o Better to heat moderately all day than extreme bursts
4. Insulate and Draught-Proof
o Insulate lofts and walls where possible
o Use thermal curtains or blinds
o Ensure windows and doors are properly sealed
🧽 How to Treat Mould Safely
Once you’ve tackled the source of moisture, you can clean and treat mould safely.
Step-by-step guide:
1. Wear protective gear: Gloves, goggles, and a mask are recommended
2. Use the right cleaning product: Anti-mould sprays (available in most supermarkets or DIY stores) or a solution of white vinegar and water
3. Scrub the area gently: Use a soft sponge or cloth — avoid dry brushing, which spreads spores
4. Let the area dry completely
5. Repaint with anti-mould paint, especially in recurring areas like bathrooms
⚠️ Never paint over mould without cleaning it first — it will grow back and potentially worsen.
🛑 When to Call a Professional
You should seek professional help if:
• The mould keeps returning even after treatment
• There’s visible water damage, leaking pipes, or rising damp
• The affected area is larger than one square metre
• You or someone in your home is experiencing health symptoms
Professionals can assess for penetrating damp, rising damp, or hidden leaks, and provide long-term solutions like improved insulation or ventilation systems.
🏘️ Advice for Renters and Landlords
Renters:
• Report mould and damp issues to your landlord in writing
• Maintain ventilation and heating where possible
• Document mould with photos if it poses a health risk
Landlords:
• Investigate reports promptly
• Ensure the property meets UK legal standards for damp and mould prevention
• Install extractor fans and maintain good insulation
• Use mould-resistant materials in kitchens and bathrooms
Recent government guidance is putting more pressure on landlords to address mould issues seriously — especially after high-profile cases involving health risks.
Mould vs. Condensation – Know the Cause, Solve the Problem
In many UK homes, condensation is the silent culprit that leads to mould. But with proper ventilation, consistent heating, and regular checks, it’s a problem you can manage — and even prevent altogether.
If you’re unsure whether the black patches on your wall are from condensation or a bigger structural issue, don’t wait for it to worsen. Take action early, and if needed, bring in a professional.
Your health, your comfort, and your home’s value may depend on it.
