How to Treat Rising Damp

Rising damp is one of most talked about and controversial types of damp. Putting aside the debates for a moment, if you think you might have an issue with rising damp you are in the right place. This How To guide takes you through identifying rising damp, the causes and how to effectively deal with it. A large part of this guide is given over to correctly identifying rising damp in your home, telling it apart from much more common damp issues. We also bust some myths around rising damp and its treatment.

What is Rising Damp?

Rising damp is a relatively rare form of damp that affects the walls of buildings. It occurs when moisture from the ground travels up through the walls by capillary action. This means that ground water is effectively sucked up through tiny tubes in the bricks, like a series of straws. This water contains salts that also travel up through the wall.

Around the affected wall, you get other porous building materials such as plasterwork and the timber found in the floor boards, joists and skirtings. These materials will also absorb the ground water easily and you may find evidence of wet rot in the timber. Read our guide for help diagnosing and treating wet rot.

Generally rising damp is first noticed by the damage it causes to the internal walls of a building. Plaster and paint can deteriorate and any wallpaper tends to loosen. A visible stain often appears on the wall in the form of a tide mark at the point where the ground water has reached. You may also see salts blooming on the internal surface. This is something often associated with rising damp and will lead to the deboning of paints and even plaster work. Externally, mortar may crumble and white salt stains may appear on the walls. We will go into the common signs of rising damp in more detail later in the guide.

Causes of Rising Damp

Most buildings have some form of barrier installed at the lower level of the wall to prevent water rising up in this way. It is called a damp proof course (DPC). These can be made of non-absorbent, water-resistant materials such as slate, bitumen and plastic depending on the period the property was built. Sometimes these physical DPCs may fail over time; in older houses they may not exist at all. If you don’t have a DPC or there is evidence that it has failed then there is nothing to prevent the water from travelling up your wall.

Sometime the DPC can remain intact, but the DPC can be bridged. This is where the damp from the ground is able to travel up past the DPC because of a construction fault.

EXAMPLES OF THIS INCLUDE:

• Debris in the wall cavity or subfloor void.
• Internal or external renders / plasters overlapping the DPC
• External ground levels being raised above the DPC.
• Inappropriate insulation material in the cavity.
• Solid floors
• Intersecting masonry structures / abutting garden walls.