Understanding Penetrating Damp, Causes and Solutions

Understanding Penetrating Damp, Causes and Solutions

10th February, 2023

Understanding Penetrating Damp: Causes and Solutions

Penetrating damp, also known as lateral damp or water ingress, is one of the most common causes of damp in a property. Although it generally affects older homes, it can occur in homes of any age depending on their construction and other factors. In this article, we discuss what it is and its causes so you can understand it better.

What is Penetrating Damp?

Penetrating damp is the process where moisture moves from the exterior to the interior of the home. It occurs when water penetrates the house through a construction deficit or when some part of the structure has been degraded to the point where it becomes porous or lets water into a property some other way.

Penetrating damp occurs mainly through the wall where the masonry and bricks become saturated with water and let it into the property. This is because their internal structure makes them act like sponges and they absorb a lot of moisture. Such damp penetration is easy to notice as you will see a damp patch on the interior. The patch leads to discolouration, wallpaper and paint peels, and flaking.

In addition to the degradation of the structure, penetrating damp can cause other issues such as frost damage, increased heat loss and thus higher energy bills, and moss growth.

While penetrating damp is typically caused by factors associated with the walls and the property’s overall construction, it has other causes too. We discuss these below.

Cracked Render

Rendering is the process of applying a cement or lime coat to the external walls of a property. Rendering makes the property look better, but, more importantly, it helps make the walls less porous thus reducing incidences of penetrating damp.

A mixture of lime and cement is common because cement gives the render strength while the lime makes it breathable. This allows water to escape, with the waterproof properties of the render protecting the walls from condensation and damp.

Cracked render loses its waterproof properties leading to penetrating dampness in a house. In addition to ensuring the rendering is done properly, incorporating fibreglass in the render can increase flexibility. This flexibility stops the render from cracking, which can happen due to temperature changes over a long period.

Render does require some maintenance to ensure it continues protecting the home as required. However, this maintenance is minimal, and the main thing to do is wash it every few years. Since the render is waterproof, it can be rinsed off by rainwater, but it will need a thorough wash from time to time as mentioned.

Bad or Degraded Pointing

Another common cause of penetrating damp is bad or degraded pointing. The bricks used in many homes are porous depending on the material used and how they are manufactured.

Bricks have capillaries that suck up a lot of water, which necessitates that the bricks be coated to prevent this absorption. However, water can still seep into the home through the top and bottom of the bricks, the sides that are usually joined using pointing, where there is no waterproof layer.

But what is pointing? Pointing is the finish applied to the mortar that sits between bricks to join them together. Pointing acts as a waterproof barrier between the masonry and exterior elements. It protects the mortar and the brickwork from rain and the damage it does.

Although cement is the material of choice for today’s projects, it is common for homes built before 1920 to have lime pointing instead. If you are thinking of buying a property and are unsure of the type of render used, you can commission a pre-purchase survey which will let you know in addition to giving you additional details about the property.

Pointing can lead to penetrating damp if it is not installed correctly or degraded. Degraded pointing can also lead to damaged brickwork, which makes the penetrating damp issue worse. This happens when water seeps into the bricks and expands and contracts as the temperature changes.

The issue might start as small cracks but can gradually get worse as the brickwork degrades, more water seeps into the bricks and causes further damage.

Leaking Windows and Doors

Building defects such as defective seals around the windows and doors can also cause penetrating damp. This issue can also be caused by poor masonry where the masonry degrades and leaves gaps between the wall and the window or door.
Damaged brickwork that causes a gap between the bricks and windows or doors can also cause penetrating damp. These structural issues should be resolved as quickly as possible to prevent the effects of penetrating damp. If you have this issue, you can get in touch with a damp proofing London specialist to come to have a look at the issue and provide viable solutions for eliminating it.

Faulty or Damaged Rainwater Goods

Rainwater goods refer to downpipes and gutters. Gutters and downpipes are supposed to work together to keep water away from your walls and to direct it away from the home. When they fail, they cause water to cascade down the wall. If this happens for long enough, you could have penetration damp issues.

Both of these rainwater goods typically fail due to a lack of maintenance or corrosion. The use of PVC has mostly eliminated the last issue, but we do continue to see poor maintenance leading to their failure. Gutters can fail due to blockages whose effects become more pronounced when there is heavy rain. Their failure leads to the walls being saturated with water and thus the penetrating damp issue you may be having.

Downpipes can be damaged in numerous ways, including through human action or corrosion in the case of cast iron downpipes. The result is the same as that of damaged gutters; the walls get saturated with water.

The penetration of water into a home resulting in penetrating damp is a serious issue. Penetrating damp causes damage, but can also lead to mould growth, which is a significant issue in itself. It is a good idea to have regular home inspections so a specialist can check for damp and alert you of the next steps.