The Causes and Cures of Rising Damp

11/11/2019

Rising damp is a relatively rare type of damp that generally affects the walls of buildings. It is formed when moisture from the subfloor level of the building travels upwards by capillary action through the walls. This is comparable to ground water getting sucked upwards by a series of straws placed within the bricks. Along with that water, the salt present in it also travels upwards. If there are porous building materials such as timber, skirting, joists, or floor boards around the affected wall, these materials also tend to absorb ground water.

In most instances, rising damp is noticed first in the form of a building’s damaged internal walls. The paint and plaster of a rising damp affected wall gets deteriorated, and its wallpaper loosens and ultimately gets detached. You may also notice a visible stain in the form of a tide mark, indicating the highest point reached by the ground water. Blooming salts may also be seen on the internal surface of the wall. In the external surface of the walls, crumbling mortar and white salt stains are the most common results of rising damp.

Causes of Rising Damp:

Most of the buildings are equipped with some kind of a barrier at the wall’s lower level to prevent the upward movement of water. These barriers are known as DPC or damp proof course. Most of these barriers are made of plastic, bitumen, slate, or other water-resistant materials. Over a period of time, the damp proof courses may fail. In some of the older houses, a DPC may not exist at all. At times, a damp proof course may get bridged, even though it is intact. This happens mostly because of construction faults, and allows damp to travel upwards past the damp proof course.

Some other common causes of rising damp are

• Inadequate sub-floor ventilation is another leading cause of rising damp. If the ventilation in the subfloor is not sufficient, humidity tends to build up. This means very little evaporation can take place from the base wall and soil.
• Obstructions in the subfloor can also lead to rising damp. Proper ventilation across the subfloor may get obstructed by the presence of debris in the sub-floor. This helps bridge the damp-course and contribute to dampness.
• In some cases, rising damp is also caused by damaged gutters and pipes as well as a poorly designed drainage system. If the drainage system of the house is not properly designed, all the water from the adjoining areas may get directed underneath the house. Dampness problem may also arise due to excessive leakage of roofs, gutters, and pipes.

Elimination of Rising Damp:

Naturally, the cures of rising damp require addressing the factors that are responsible for its formation. Mentioned below are some of the best ways to deal with this problem.

DPC Related Problems:

• If the problem has been caused by a damaged damp proof course, you will have to repair or replace the course. Deterioration of the courses generally takes place over a period of time because of movements. Some of the visible signs of a damaged DPC are a white, powder like residue on the surface and timber rot. If the rising damp is seen in isolated patches, insert a new damp proof course and ensure that the deteriorated plaster is adequately treated.
• In some instances, brick walls are built much higher from the ground than what is required as per the regulation. In these circumstances, if the underfloor ventilators are blocked or the external ground level is raised, the moisture has nowhere to escape. Therefore, the only fix to this problem is removal of soil.

Subfloor Ventilation Issues:

• Installation of ducts connected to sub-floor vents in areas where blockage has been noticed by laying a platform higher than its original position.
• Replace all traditional vents made of cast iron and terracotta with their advanced counterparts capable of delivering a higher ventilation area.
• In houses that are fully made of brick, create vents in the internal base walls to ensure free air flow throughout the subfloor.
• Create flues in suitable locations so that the air from the sub-floor area is drawn out by the stack effect.
• In order to move more air, wind-driven cowls may be placed on the top of the flues.
• Use subfloor ventilation fans to ensure unobstructed air flow across the subfloor area.

Sub-floor Obstructions:

• If there is a concrete path above the level of the DPC, rebuild it below the damp-course and make sure its slope is directed away from the building.
• Consider installing an enclosed drain adjacent to the wall and connecting it to the stormwater.

Damaged Pipes and Gutters:

• Test your pipes, gutters and pipes for leaks and fix them, if required.
• If this doesn’t solve the problem, check for damaged or cracked wastepipes.

If you are facing rising damp or any other subfloor related issues, please contact us immediately for guaranteed solution. We specialise is designing and installation of sub-floor ventilation systems that provide effective and long-term moisture control for building foundations.