What Causes Rising Damp? Everything You Need to Know

​Rising damp is a common and frustrating problem, especially in older buildings. It can cause peeling paint, crumbling plaster and even long-term structural damage. But what is rising damp, and more importantly, what causes rising damp? Understanding how and why it occurs is the first step toward resolving the issue for good.

Groundwater Rising

Rising damp occurs when moisture from the ground travels upward through a wall by capillary action. The small pores in brickwork and mortar act like tiny tubes that draw water into your home and are so effective they can even work against gravity.

As the water rises, it carries salts and minerals from the soil up through your walls. When the moisture evaporates, these salts remain on the surface, leaving white, powdery marks on the inside and outside of your property. Over time, this rising groundwater can cause plaster to flake and paint to bubble.

Typical signs of rising damp include dark patches near skirting boards, a musty smell and deterioration of wall finishes. Left untreated, it can spread and damage timber, flooring and structural materials.

Missing, Damaged Or Bridged Damp Proof Course

Most modern homes include a damp proof course (DPC). This is essentially a horizontal barrier built into the wall that stops water from rising. However, if the DPC is missing, damaged, or bridged, it can no longer do its job.

A bridged DPC happens when moisture bypasses the barrier, often due to high external ground levels, internal plaster that extends below the DPC, or debris trapped in the wall cavity. In older homes, the DPC may have deteriorated over time, allowing water to rise freely into the structure of your property.

Poor Drainage

Poor drainage can make rising damp worse by keeping the ground around your home constantly wet. When rainwater cannot drain away efficiently, it builds up near the foundations, increasing the amount of moisture that’s available for absorption.

Blocked gutters, broken downpipes or uneven paving that slopes toward the house can all contribute to the problem. Raised flower beds or driveways built against exterior walls can also trap water.

To reduce risk, ensure that surface water drains away from your property. Keep gutters clear, repair damaged pipes, and if needed, install drainage channels or French drains to redirect water away from the walls. Good drainage is one of the simplest yet most effective ways to protect your home.

Porous Materials

Older buildings are particularly prone to rising damp because of the materials used in their construction. Traditional lime mortar and soft bricks are highly porous, meaning they absorb and hold moisture easily. Over the years, weathering and frost can widen cracks and pores, allowing even more water to travel through.

Repairing damaged brickwork and repointing with the correct materials can help reduce water absorption. Using breathable paints and plasters allows walls to release moisture naturally, preventing it from becoming trapped inside the structure.

Condensation

While condensation is not the same as rising damp, it can make damp conditions worse. When warm, humid air meets a cold wall or window, it cools and releases water droplets. If these droplets form on already damp walls, they can keep the surface wet and encourage the growth of mould.

Condensation is often caused by poor ventilation, blocked air vents, or insufficient insulation. Everyday activities like cooking and showering can increase indoor humidity, especially if air cannot circulate properly.

Improving airflow is key. Open windows when possible, use extractor fans in kitchens and bathrooms, and keep vents unblocked. Dehumidifiers can also help control moisture levels and dry damp areas.

How To Stop Rising Damp

Identifying the exact cause of damp can be challenging, as symptoms of condensation, penetrating damp and rising damp often overlap. A professional survey is the best way to determine the source of the issue and find the right treatment.

Solutions may include repairing or replacing a damaged damp proof course, injecting a chemical damp-proof barrier, or improving drainage and ventilation. In older buildings, breathable materials and sympathetic restoration methods can help control moisture without harming the structure.

Insulating your home can have a big impact on damp as well-insulated homes are less likely to suffer from condensation. Properly insulating your doors and windows and changing to energy efficient doors and windows can also help to prevent cold spots that could make condensation worse.

Next Steps

If you notice signs of rising damp, don’t ignore them. A thorough inspection and targeted repairs can make a lasting difference. By learning how to stop rising damp, you can protect your property’s structure, improve indoor air quality, and preserve the value of your home for years to come. If you're concerned about rising damp or would like expert advice, we're here to help, please contact us.

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