Rising Damp

What is rising damp?

Rising damp is the process of water rising vertically up from the ground and travelling by capillary action through porous material such as bricks and mortar. This will cause the wall to become damp as hygroscopic salts travel into the brickwork and plaster. As water evaporates, it these salts that are deposited into the wall attracting more moisture from the atmosphere.

As the process continues, the wall and surrounding area becomes more saturated and signs of rising damp will become evident such as crumbling of plaster and white tide marks appearing on a wall up to a height of around 1 metre.

Problems such as dry rot, wet rot and wood boring beetle infestations are also more likely to occur as surrounding timbers become saturated. It is a slow process and can be present for many years before any sign of a problem appears.

Why does Rising Damp typically occur?

Rising damp occurs due to:

  • No damp proof course (DPC) as is commonly the case with older buildings
  • Deterioration and failure of the DPC over time
  • Changes in external ground levels meaning the DPC becomes bridged. For example, if a new patio has been laid
  • Moisture travelling in between the wall and the render so bypassing the DPC.

What are the signs of Rising Damp?

Rising damp will only appear at ground level.  Signs include:

  • Tide mark on an internal or external wall most commonly no more than 1 metre from the ground
  • Internal plaster that is bubbling and crumbling
  • Peeling wall paper
  • Damp looking patches showing on wall paper or plaster and above skirting boards
  • White marks or damp arches on external brickwork or render.
  • A musty smell

How do we treat Rising Damp?

Our survey assessment will decide the best course of action. This could involve clearing overgrown vegetation, to fixing a leaking pipe but in certain circumstances the application of a damp proofing system and removing plaster that has become affected by moisture is unavoidable.

Above Ground Damp Proofing System

A chemical injected damp proof course is used to form a barrier to moisture. It involves drilling into each brick at calculated intervals and then injecting a silicon fluid or gel. This forces a chemical into the brick which creates resistance to moisture. The height of where you inject is determined by the site conditions such as external ground levels, type of brick and internal sub-floor levels.

The treatment usually takes place from the inside as external renders and plinths can make it difficult to do from the exterior of a property. As part of a damp proofing system, contaminated spoiled plaster will be removed and replaced using a specialist re-plastering specification.

Below ground damp proofing system

Cementitious tanking or waterproof cementitious membrane is another form of damp proofing used in circumstances where ground levels cause the possibility of lateral penetrating damp such as where there is internal suspended timber floor or solid floor lower than the high ground and/or where there is a bridging of the damp proof course.

A cementitious membrane uses a cement based chemical slurry which when plastered onto the wall reacts and penetrates the prepared surface to prevent water moving through earth retaining walls. This method can work in conjunction with a chemical DPC system and will be applied below the injected damp proof course to protect the skirting and sub floor timbers.

Cavity drainage is another method of below ground waterproofing using plaster sheeting membrane, drainage and pumps and more commonly used in basement waterproofing projects. Further information about our below ground and basement waterproofing solutions can be found on our Basement Waterproofing pages.

Other treatments

Other treatments may also be necessary as a result of the damp conditions and to provide ongoing protection to the property.

This may include timber treatment for woodworm, treating a dry rot outbreak and treatments that will protect the property from water penetration in the long term such as applying water repellent masonry protection cream to give a wall more resistance to water.

Our goal is to provide the right solutions that provide the best long term protection for the property.

More information can be found on our Timber Treatment page.

TIMBER TREATMENTS

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