Dampness Diagnosis & Treatments

Monday February 12th, 2018

Damp patches on walls after rain - What could it be?

After a day or more of heavy rain, we hear from a great number of homeowners and facility & asset managers that they have noticed damp patches on the walls.

There are many causes of excess moisture in the structure of a building, such as leaking pipes and damage to gutters and roofs. However, a high proportion of damp problems in buildings are caused by rain penetration, condensation or rising damp.

Diagnosing the cause of dampness in a building is vital so that correct treatment and repair can be carried out to address the source of the problem.

When the diagnosis is wrong, the treatment fails and the damp issue remains.
Many of the visual signs of the three main categories of damp in buildings may look quite similar to the untrained eye. This is why penetrating damp and condensation can be mistaken for rising damp or vice versa.

There are 3 main categories of dampness

  • Penetrating Damp
  • Condensation
  • Rising Damp

For each different category of dampness and the cause thereof, a different solution of remedial treatment and repair is required.

1.Treating Penetrating Damp

If the cause of the penetrating damp has been identified as failing guttering, window / door frames or roofing, these need to be repaired as well as replacing damaged plaster and timber work.

If the water is entering through the wall to floor joint, an effective and lasting remediation is to inject the joint with flexible hydrophilic polyurethane along the length of the wall to floor joint.

The hydrophilic polyurethane grouts seek out water in a crack, they absorb into tight cracks and pores bonding to the wet concrete - creating a very effective and long-term solution in stopping leaks via a concrete crack or construction joints.

2.Treating Condensation

If the cause of the damp has been identified as condensation, the cure may be as simple as installing a good quality ventilation system that encourages movement of the air from inside the building to the outside. Damaged plaster and timber work need to be repaired or replaced.

3.Treating Rising damp

This treatment involves injecting a damp-proof course (DPC) into a location where no physical DPC is present.

Holes are drilled at regular intervals. The distance between the holes will vary depending on certain variables such as the type of brick, cavity and how far the product travels when injected. The holes are then filled after the process is completed.

The product works by lining the pores of the substrate to reduce their size so water can no longer pass through, but air still can. The method works on moving cracks, wide gaps or voids.

More about common signs and how to treat damp walls...

This article was contributed by Anne Nilsen of Waterstop Solutions.