Penetrating Damp near Window

If you walk into a room and can spot any of the following issues, chances are you have what is known as penetrating damp.

  • Musty walls
  • Wet walls
  • Peeling paint/plaster/wallpaper
  • Mould spores on the walls
  • Staining on external walls

Left untreated, penetrating damp can cause significant deterioration to your property’s infrastructure, damaging walls, floors, and ceilings, and eventually seeping into the timbers causing dry rot.

You are more likely to suffer from penetrating damp if your property has a basement that is vulnerable to sitting groundwater. The groundwater will penetrate the porous building materials, seeping further into the fabric of the building as its structure becomes more and more waterlogged.

Penetrating damp can also occur if your property has defective window or door seals, guttering, or roof tiles.


Inviting a Garratt’s surveyor to check for damp could save your property from future damage and excessively costly remedial work.

The surveyor will check the property’s weak and vulnerable areas where water ingress is more prevalent and prepare a full report and costings to eradicate the problem completely. Garratt’s does not do a quick fix for any penetrating damp issues – to resolve the problem permanently Garratt’s will recommend a solution that eliminates all future penetrating damp risks.




What is the difference between rising damp and penetrating damp?

Penetrating damp is caused by water penetrating the external brickwork of a building at any level and seeping through to the internal walls. This can come, for example, from blocked gutters and downpipes, a leaking roof, and groundwater.

Rising damp can occur as the result of an ineffective damp course. Your brickwork will be soaking up groundwater like a sponge creating a distinctive ‘tide mark’ around the ground floor external walls.

What damage is done to a property if left untreated?

The damage is widespread. Paint will blister off the walls. Unhealthy, odorous mould will grow across the internal walls. Moisture will seep into the building’s infrastructure causing deep-seated long-term damage. Floorboards will rot. Both wet and dry rot can set in.

Will rendering stop penetrating damp?

While rendering will provide a temporary fix if the source of the damp is not tackled, then eventually the damp will break through the render and continue to spread its damage. If penetrating damage is diagnosed in a building with a basement, Garratt’s will always recommend installing a basement tanking system to guarantee the permanent eradication of penetrating damp.

How much does it cost to stop penetrating damp?

The cost will vary depending on the severity of the damage, the size of the building, and the most suitable treatment option. Garratt’s usually recommends either a Type A waterproofing system or a Type C.

What is a Type A basement tanking system?

Type A basement tanking is a good preventative measure and is ideal in situations where basement walls are fragile or unstable. It’s also a good option if there aren’t excessively high levels of sitting groundwater. In essence, Type A basement tanking involves adding a waterproof barrier to the walls, which stops water from penetrating the internal face of the walls.

What is a Type C basement tanking system?

In contrast, Type C basement tanking involves installing a sump and pump system around the property that directs ingressed water away from the basement completely. It doesn’t put any extra strain on the property’s structure and is ideal in areas where there is a lot of sitting groundwater.

What if my property does not have a basement?

If penetrating damp isn’t in the basement and is instead around your windows, doors, or near your guttering, you will need to repair these issues separately. Garratt’s Damp & Timber generally do not treat penetrating damp outside of basements.

To book a free survey or submit an enquiry about fixing penetrating damp in your home, please use the form below:

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