What causes damp in my home?

Condensation – the most common cause of damp and mould

Condensation occurs when warm, moist air meets cold surfaces like windows, walls, or ceilings which leads to water vapor turning into liquid droplets. This is the most common type of dampness, especially during the chilly winter months in homes without proper insulation or ventilation.

Reasons for condensation at home

Condensation tends to form in areas of your home that are more exposed to moist air, particularly in bedrooms, bathrooms, and kitchens. This is especially noticeable in winter when heating systems are in use.

Here are some common factors that might be contributing to condensation:

• Cooking, boiling kettles, showering, and drying clothes indoors
• Insufficient ventilation in kitchens and bathrooms
• Poor insulation that results in cold surfaces and mould growth
• Blocked or missing air bricks, or windows without trickle vents

How to spot condensation

The good news is that spotting condensation is straightforward which can help homeowners tackle mould and dampness before it becomes a bigger issue. Keep an eye out for signs like:

• Water droplets forming on windows in the morning
• Black mould appearing on walls, ceilings, and around window frames
• Damp patches on internal walls
• Peeling paint or wallpaper
• A persistent musty smell in certain rooms

Solutions to condensation problems

If you’ve noticed any signs of condensation or mould, there are several solutions and preventive measures you can take to keep your property well-maintained:

• Improve ventilation – use extractor fans, open windows, or install trickle vents
• Utilise a dehumidifier in areas with high moisture
• Add insulation to minimise cold surfaces and thermal bridging
• Try to avoid drying clothes indoors whenever possible

What is rising damp?

Rising dampness in walls occurs when groundwater seeps up through porous building materials like brick and mortar, thanks to a process called capillary action—essentially, water moving upward through tiny channels in these materials.

While it’s not as common as condensation or penetrating damp, it can lead to serious structural issues if not addressed quickly.

Rising dampness causes

Unlike condensation or penetrating damp, which typically affect specific areas or come from outside water sources, rising damp starts from the ground and works its way up through the walls.

Understanding what causes rising damp can help you spot its signs and maintain your property long-term:

• A missing or ineffective damp-proof course (DPC)
• Soil, debris, or raised ground levels that bridge the DPC
• Blocked or filled wall cavities that allow water to travel upwards
• Old buildings with faulty or worn-out waterproof membranes

Rising dampness signs

Rising damp in walls can look a lot like other moisture problems, but it has some distinct signs that homeowners should look out for:

• Tide marks on the inside walls (usually no more than 1 metre high)
• White, salty deposits (efflorescence) on surfaces
• Peeling paint or damp, crumbling plaster
• Wet or rotting boarding and floor timbers
• Musty or damp smells near the ground, especially in older homes

Rising dampness treatment

To tackle rising damp, you need to address both the moisture source and any damage it has caused. Since some symptoms can be confused with condensation or penetrating damp, getting a professional diagnosis is crucial.

The first step is to have a qualified surveyor check the property to confirm if rising damp is the issue.

Once that’s sorted, solutions for rising damp may include:

• Making physical or chemical adjustments to the DPC, based on the surveyor’s findings and expert advice
• Lowering external ground levels to ensure soil or patio surfaces are below the DPC
• Cavity cleaning to remove debris or other porous blockages that could be bridging the damp course and allowing water to rise above it

What is penetrating damp?

Penetrating damp essentially occurs when water from outside finds its way into a building through the walls, roof, or other parts of the structure.

Unlike rising damp, which moves up from the ground, penetrating damp spreads horizontally, often due to structural issues of the building or exposure to harsh weather.

This type of damp can affect any area of a property, but it’s particularly common in older homes or those that face heavy winds and rain.

Penetrating damp causes

Unlike condensation, which is more prominent in winter due to big temperature differences inside the home, penetrating damp can be seen at any time of the year, especially after heavy rain. It often arises from structural problems, such as:

• Damaged or missing roof tiles and flashing
• Cracked render or brickwork
• Blocked or broken gutters and downpipes
• Poorly sealed window or door frames
• Faulty pointing

Penetrating damp signs

Since penetrating damp is linked to structural issues or properties that are frequently exposed to bad weather, the signs can become more obvious after heavy rain that seeps into cracks or crevices. You might notice:

• Damp patches on interior walls or ceilings that darken after rain
• Localised mould growth or peeling paint
• Dampness around windows or external walls
• Staining or blistering on plaster and paint

Penetrating damp solutions

Just like with rising damp, it’s essential to pinpoint the source of the water intrusion and fix it as soon as possible. Having a specialist carry out a survey will provide the most accurate diagnosis, along with the necessary repair and prevention steps.

Once you’ve sealed all the vulnerable areas, let the space dry out completely, the period of which can vary depending on how severe the damp is.

To keep your property in good shape, make sure to regularly:

• Inspect and repair the roof and gutters
• Repoint or reseal brickwork and render
• Ensure windows and doors are properly sealed