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Why are My Walls Wet After it Rains?

Damp in the home or business premises can make living and working conditions uncomfortable, as well as potentially unsafe if the root cause is left untreated. There are many reasons why you might be experiencing damp in your property. For example, rising damp in your London home can occur from a missing or damaged damp proof course. However, if you have noticed that your walls are wet on the inside after a bout of heavy rain, you may well be suffering from an issue known as penetrating damp.

damp-wallWhat is Penetrating Damp?

Penetrating damp is the name given to the movement of water from exterior facades to interior surfaces. It can occur after particularly heavy rainfall in properties with solid brick construction, properties without an insulating cavity or if the cavity has been incorrectly filled. If a cavity has been filled with inappropriate material, it can soak up and hold a lot of moisture which slowly permeates into interior walls, causing wet patches on the wall after rain.

This type of damp can also be caused by leaky gutters that are broken, wrongly installed or incorrectly sized for the property which causes water to be directed to the wall instead of away from your home. Similar problems can occur from cracked or broken rendering and brickwork, or if windows have been installed badly or the sill has been damaged, directing water onto the wall below instead of funnelling it away from the house.


When is Penetrating Damp Most Common?

Penetrating damp is also likely to occur on exterior walls where the ground level is above the interior walls, creating a “bridging” effect for moisture to avoid the damp proof course and easily travel from exterior to interior surfaces. However, if the walls wet with damp are above ground level or in higher-storey properties, it is likely to be caused by faulty brickwork, either due to damage caused from frost, age, deteriorating mortar joints or due to roof or rainwater goods defects.

What are the Signs of Penetrating Damp?

If you suspect that your property may be suffering from penetrating damp, you are likely to see the following signs around your property:

  • Wet patches on walls that grow in size after rain
  • Damp patches that occur on any part of the wall (high or low)
  • Peeling or blistering of wallpaper or paint
  • Discoloured paintwork or wallpaper
  • Crumbling or blistering of plaster

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    What Happens if Left Untreated?

    Without solving the source of penetrating damp, whether caused by defective cavity insulation, leaking gutters or broken brickwork, the problem will continue to persist and can lead to some severe problems around your property, including:

    • Wet rot
    • Structural problems
    • Mould growth
    • Salt deposits (which cause increased moisture ingress)
    • Timber decay

    Unless there is an obvious source of moisture, property owners can often misdiagnose the type of damp that is affecting their structure, which can lead to costly and inefficient DIY repairs. If you are concerned about penetrating or rising damp in your London-based property, please don't hesitate to give our expert and friendly team a call on 0208 535 7536 for a free survey.
    4:04 PM Sep 22nd|@garrattsdamp
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