What Causes Mould on Walls And How Homeowners Can Get Rid Of It

Mould on walls is a common issue in homes across the UK, especially in properties exposed to damp weather or with poor ventilation. It appears as dark patches, often accompanied by a musty smell, and while it may seem like a cosmetic issue, it can also affect indoor air quality, cause a range of health problems and even affect the structure of your property. Understanding what causes mould on walls is the first step to tackling it effectively and preventing it from coming back in the future.

Excess Moisture

Mould thrives in moist areas. Leaks, rising damp or water seeping in from outside can create the perfect environment for mould to grow. Even small leaks from pipes, roofs or windows can lead to hidden damp spots.

Rising damp is another common cause, particularly in older buildings. It happens when moisture from the ground travels up through bricks or mortar because the damp-proof course (DPC) is missing, damaged or bridged by high ground levels. This leaves lower sections of walls constantly damp, which provides ideal conditions for mould to grow.

Water ingress from cracked render, damaged roofing or overflowing gutters can also allow rainwater to soak into walls. Regular inspections and prompt repairs can go a long way toward keeping the moisture levels in your property under control.

Poor Ventilation

Lack of airflow is one of the main causes of mould. Moisture from everyday activities like cooking, showering and drying clothes builds up in the air. Without proper ventilation, humidity levels rise and condensation begins to form on cooler surfaces such as walls and windows.

Kitchens, bathrooms and laundry rooms are particularly at risk. To prevent this, open your windows regularly, use extractor fans and keep internal doors open to allow air to circulate. In rooms without windows or natural airflow, a dehumidifier or mechanical ventilation system can make a big difference.

Condensation

Condensation is another common cause of mould, especially during winter. It occurs when warm, moist air meets a cold surface and cools quickly, turning into droplets of water. These droplets often collect on walls, ceilings or behind large furniture items, where the lack of ventilation traps moisture.

Over time, the damp created by condensation allows mould to develop. Improving insulation and ensuring good ventilation will help keep surfaces warmer and prevent moisture from settling.

Insufficient Insulation

Poor insulation often leads to cold spots on walls where condensation can easily form. This can lead to moisture build up and result in the growth of mould. This problem is common in older houses that lack cavity wall insulation or in homes where insulation has degraded over time.

Upgrading insulation helps maintain stable indoor temperatures and reduces condensation. Options such as insulated plasterboard or wall insulation can prevent cold walls, reduce energy bills and make rooms more comfortable.

Maintenance Issues

Sometimes mould is caused not by humidity inside the home but by maintenance problems outside or within the structure. Blocked gutters, cracked roof tiles or faulty flashing can all allow rainwater to enter your walls. Similarly, plumbing leaks behind walls or under floors can create damp patches that remain hidden until mould appears.

Regularly checking the roof, gutters, windows and pipework can help prevent these issues. Cleaning gutters, repairing cracked pointing and fixing leaks promptly will reduce the risk of trapped moisture and mould growth. Good maintenance is one of the simplest but most effective methods of keeping your walls dry and healthy.

How to Get Rid of Mould on Wall

Once mould appears, it's important you remove it safely and fix the underlying problem. Simply wiping mould away without addressing the source of moisture will only provide a temporary fix.

Start by identifying the cause, such as a leak, condensation or poor ventilation, and take steps to eliminate it. For small patches, you can clean the affected area using warm water and mild detergent or a specialist mould cleaner. Always wear gloves, avoid dry brushing and keep the room well-ventilated during cleaning to prevent spreading spores.

If the mould problem is more extensive or keeps returning, professional help may be needed. A damp specialist can assess the root cause and recommend lasting solutions such as improved ventilation or upgraded insulation. Knowing how to get rid of mould on walls safely and thoroughly ensures the problem doesn’t return.

How to Prevent Mould on Walls

Prevention is always better than cure when it comes to mould. Keeping humidity under control, improving airflow and maintaining your property all help reduce the risk of mould growth.

If your home has persistent cold spots or high humidity, consider upgrading insulation and installing extractor fans. Using dehumidifiers and keeping heating consistent can also help. Learning how to prevent mould on walls is key to maintaining a healthy indoor environment and protecting your property’s structure.

Understanding what causes mould on walls will help you to take practical steps to stop it before it becomes a serious problem. Knowing both how to get rid of mould on walls and how to prevent it ensures your home stays clean, healthy and efficient for years to come.

Next Steps

If you’re struggling with mould at home, we’re here to help you eliminate it for good. As specialists in eco-friendly home improvements, we provide personalised advice and effective insulation solutions that target the root causes of mould, keeping your home healthy, comfortable, and protected for the long term. Get in touch with you. Image source: Canva