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Penetrating Damp: Unveiling the Hidden Threat to Your Home

Updated: Oct 3, 2023

Damp issues can be difficult to diagnose correctly. Often, different causes of dampness can produce similar symptoms in the building, and care must be taken to ensure that the source of the problem is properly identified.


One of the most common causes of damp issues is known as "Penetrating Damp." But what is it, what are the causes, and how do you fix the problems it creates?


damp wall due to leaking gutter

What Is Penetrating Damp?

Penetrating damp is the term used to describe the ingress of water into a building from external sources. Unlike condensation, which is caused by internal environmental factors, penetrating damp is caused by moisture penetrating through the fabric of the building in some way, either above the DPC (Damp Proof Course), or below it.


What Are the Common Causes?

The causes of penetrating dampness can be wide-ranging, with some easy to identify and fix, while others are less so. A surveyor will carry out a thorough check of both the external and internal areas of the building to see if any obvious defects are present that could be one of the sources of moisture. Some of the obvious signs of penetrating dampness are listed below:

  1. Holes in the Roof: Are there any obvious locations where water could be entering the building from above, such as a broken roof tile or a tear in a flat roof membrane?

  2. Walls: Is there any green algae growing on the wall that could indicate a leaking gutter, downpipe, or overflow? Are there any cracks that could possibly allow water to penetrate the wall?

  3. Ground Levels: Does the ground level seem high compared to the DPC? This can allow water to affect the walls in the habitable part of the building.

  4. Damp Patches & Stains: Is there a damp patch on a wall, ceiling, or floor in the vicinity of any defect noted outside?

  5. Peeling or Bubbling Paint: Is there any paint bubbling or peeling on an internal wall? Are there any salt crystals present that could indicate an active damp issue?

  6. Musty Odours: Is there a musty or damp smell in the air internally? Even if there is no visible sign of a damp issue, a damp smell can prompt further investigation to identify a potential problem.

  7. Rot & Insect Attack: Is there any sign of rot or wood-boring insect infestation on structural timbers, such as joists or rafters? If the moisture content of timber is allowed to get above a certain level, it can become vulnerable to attack by rot and wood-boring insects.

  8. Mould: Interestingly, mould does not occur as a result of a penetrating damp issue, but only if condensation is present. That's not to say that the penetrating damp issue has not cooled the wall enough to create a condensation issue as well. Often there is more than one cause of damp problems, so keeping an open mind is important.


Addressing a Penetrating Damp Issue

Addressing the problem is important to avoid a whole range of issues if it is left unattended. Consider the following steps:

  1. Locate the Source: To effectively address a penetrating damp issue, we must find the lead source of moisture. Again, keep in mind there may be more than one and a penetrating damp issue can cause other damp issues such as condensation.

  2. Repair Any Defects: Once the source is identified, undertake the necessary repairs. This may involve replacing damaged roof tiles, fixing broken gutters, lowering ground levels, or addressing any other visible defects.

  3. Treat Affected Areas: In many cases, repairing the defect and allowing the building fabric to dry naturally over time will solve the issue. However, if structural timber has been affected by rot or wood-boring insects, parts of these timber elements may require treatment or replacement.

  4. Making Good: Once the building fabric has dried, and any specialist treatment work has been completed, restore the internal finishes & decoration.

Penetrating dampness can significantly impact a building if left unattended. Identifying the signs of penetrating damp at an early stage can help minimise the extent and cost of remediation for the damage it may cause. Regular maintenance and addressing defects promptly is key to avoiding some of the extra problems damp issues cause.


While this article provides a brief overview of the problems caused by penetrating dampness, it is not an exhaustive list of recommendations. It is always wise to consult a professional damp surveyor if you are unsure about any damp issue. At Charterhouse Surveying, we can conduct a thorough investigation and provide expert advice to help resolve any issues you might have. Please feel free to contact us for advice.

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