There are many reasons why a property becomes mouldy. Joe Trivett, Damp Expert at Allerton Damp Proofing, walks us through the potential causes:

Renovation pushing in water

“In cities with high property prices such as London, every inch of space is valuable to the homeowner. Some popular ways to make the most of exterior space include patios, paving, concreting, and walls to shield the garden from onlookers. However, water will always take the path of least resistance, so solid surfaces and building work can push water into the property, where it once soaked through the ground.

“Another renovation that could cause issues are neighbouring basements or cellars being built or converted. If neighbours dig down into basements, there is less area for water to drain into, so the natural level that water sits at moves closer to the surface. In turn, if your property is already below ground, the amount of pressure the water exerts on your basement is increased. This heightens the chances of a leak.

“If a neighbour’s basement is being waterproofed or tanked, this can also push water into your basement. It’s worth checking the work neighbours are having done, especially if your property shares a wall with theirs.”

Outdated building techniques

“If the property is a Victorian-era or older build, it may have a few issues that could cause dampness. The walls and floors of properties soak up water from the ground. Most houses are built with a damp proof coursing layer just above ground level to combat this process, stopping water at the building’s base from moving up the walls. However, this often breaks down or isn’t installed in old properties, which is why Victorian houses might have damp problems that can cause mould and rot to develop at the bottom of walls and on skirting boards.”

Lack of ventilation

“Humans sweat and exhale water droplets, while daily activities such as showering and boiling water produce additional humidity. This water condensates on windows and walls, providing the perfect damp surface for mould to grow on. Plenty of ventilation is key for humid air to leave the property and allow walls and windows to dry.”

Poor Maintenance

“If you suddenly see water pool through the roof or in patches on the wall, a leak is the most likely cause. Broken guttering, lost roof tiles or a broken pipe in the wall are common causes of a sudden leak.

“If the floorboards are damp or rotted, ventilation blocks that allow air to run under the house might be blocked by debris or building work, preventing floorboards from drying out.”

Here are some tips for preventing condensation, damp and mould:

• Keep your heating on low and continuously, rather than at high temperatures that cycle between on and off.
• Ventilate rooms, opening windows in humid rooms for short periods, especially if the windows don’t have any vents.
• Install and turn on extractor fans in high humidity rooms, such as the kitchen and bathroom.
• Check the ventilation blocks which allow a light draught to flow through the property or under the floorboards aren’t blocked.
• Check guttering and roof tiles aren’t broken or missing.
• Allow space between furniture and walls, so moisture isn’t trapped and can instead dry.
• Dry clothes outdoors, or use a tumble dryer that can pump humid air outside.
• As a property buyer, get a full property survey, especially when buying an older home.

Joe Trivett, Damp Expert at Allerton Damp Proofing, adds: “Blocking up ventilation blocks and using draught blockers can be a quick way to heat your home, especially during the colder months. But the work required to treat damp may eventually swallow up the money saved on heating. A more energy-efficient approach that allows the property to ‘breathe’ and stay dry is installing more loft insulation and double glazed windows.

“In older properties, the use of a fireplace can help the building stay dry – as material combusts, the air is drawn from other areas of the house, creating a natural, warm draught that encourages drying of surfaces.”