What Causes Wet-Looking Spots on Walls?

Wet walls or damp patches can be unsightly, and even in minor cases can cause damage to wallpaper and soft furnishings. In more serious cases, moisture can damage the structure of the walls themselves or lead to significant risks to occupants' health. Damp issues might happen occasionally, on a recurring basis or may even seem to be permanent, and there are several different potential causes. It is important to investigate the matter thoroughly because it can take time to resolve the problem, and there is scope for it to do significant damage in the meantime.

Persistently damp walls are often the result of rising damp problems or other serious underlying concerns. Treating penetrating damp can be a slow process, and issues may get worse in the meantime, so you should investigate as soon as you notice symptoms like damp patches on walls or a musty smell. If left untreated, rising damp can pose the risk of health issues and, over time, cause further damage to the building structure.

Here, the rising damp treatment experts at Moisture Stop UK examine the most commonly found causes of damp patches on interior walls, and the steps that homeowners, landlords and builders can take to resolve the problem - not just in terms of addressing the symptoms, but permanently fixing the root cause of a damp problem before it gets worse.

Common causes of damp patches on walls

Wet-looking spots on walls can be a number of different underlying issues. These might be relatively minor - such as condensation, which can often be fixed relatively easily with only minor changes - or more serious. Wet walls or patches are often caused by rising damp which, as we have noted above, can represent a much more serious problem. Below, we have listed some of the most common causes of water droplets or damp areas on walls, to help you assess the problem.

Condensation

Condensation occurs when warm, moist air comes into contact with a cooler surface. It may be seen on walls and windows, and it results in the appearance of wet spots. Condensation problems are common in areas where natural air circulation is restricted, or where there is poor ventilation, such as in bathrooms and kitchens.

Damp patches on walls caused when condensation forms will usually dry on their own, but you may need to use a dehumidifier or open a window to balance the temperature. If the problem continues, it can lead to black mould growth, which poses a significant risk to health. Even when a damp patch disappears on its own, if it reappears you should investigate further, as there could be a different underlying cause.

Bear in mind that the problem could also be caused by poor insulation. Cavity wall insulation is designed to regulate temperatures and cold surfaces so that warm air inside is not affected by cold outside temperatures, but it is not always as effective as it should be.

Leaks

Water leaks from plumbing, roofs or exterior walls can cause persistent wet spots. These leaks might be caused by problems with pipes within the wall, cracked roof tiles or other damage, or poorly sealed window frames. These wet spots may grow over time, cause paint to peel, or allow mould and mildew to grow. The best way to tell that a leak is the cause of your damp issues is if the affected area is relatively small, or there are isolated patches of damp only in one spot. Similarly, if the issue arises during or after heavy rain, this could be an indication that the problem is caused by problems with roof tiles.

Finally, if you know that there are water pipes inside walls where wet spots are appearing, this could be an indication that moisture is caused by a leak. This can be a simple problem to solve in some cases, and it is worth checking whether or not the issue is caused by water ingress, heavy downpours or leaking pipes before ordering a damp survey or other investigation.

Rising Damp

Unfortunately, rising (or penetrating) damp is one of the most common causes of damp patches on internal walls. While this problem has a number of solutions, some of which are actually relatively simple, it also poses the biggest potential risks to your home and your health. Penetrating damp occurs when moisture from the ground travels up through the porous materials of a wall due to capillary action, which describes the natural movement of water molecules. This is more common in older buildings without modern damp-proofing, but even a building with a damp proof course can be susceptible to mould and mildew growth, damp spots or other symptoms of rising damp.

The most common places where this can be seen are ground floors and basements, and especially utility rooms or other areas where ventilation is poor. Spots typically start at the base of the wall, meaning that wooden skirting boards are often affected. A skirting board may experience warping, rotting or paint damage. Walls may also have a "tide mark." This mark is typically visible between three and five feet above the floor, indicating the highest point to which the damp has risen, and stains are usually brown or yellow. They may be darker along the line of the tide mark.

The moisture from rising damp can cause paint and wallpaper to peel, bubble or flake off the walls. Salt deposits, known as efflorescence, might also be visible in the form of a white, powdery substance on the wall's surface. The presence of dampness encourages the growth of mould and mildew. These fungi thrive in moist environments and can appear as black, green or grey spots on the walls. They also bring a musty or earthy smell, which is one of the key indicators of rising damp.

How can you fix damp patches on internal walls?

One of the most significant causes of damp patches on internal walls is rising damp, which is sometimes called penetrating damp when it starts to show through the walls. Caused by capillary action, which forces water up inside your walls through a combination of surface tension and adhesion, a rising damp issue needs urgent attention. Beyond leaving excess moisture on your walls, rising damp can lead to structural defects in the walls of your home, or even result in health problems due to mildew and mould growth.

There are several ways to treat penetrating damp, but the best solution is Moisture Stop UK's HS-221 system. This is a device that can be easily installed on external walls, and which uses low-frequency electromagnetic waves to counteract the capillary action of the water molecules in your home. It is the fastest and most effective solution in the UK, and is capable of completely drying a brick wall in as little as three months. Unlike a damp proof course or other solution, HS-221 gets to work straight away, and it is perfect for old buildings because it does not require any construction to install.

By addressing the cause of rising damp, you can resolve the challenges of damp patches and other symptoms of rising damp. In turn, this can prevent the structural problems and health issues that can otherwise arise. Speak to the team at Moisture Stop today to learn how the HS-221 system can help you and fix the damp issues you are experiencing.