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Dealing with damp

How to get rid of penetrating damp

By Liz Ransome-Croker

Article 3 of 7

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How to get rid of penetrating damp

We explain what could be causing your penetrating damp, from cracks in a wall to blocked cavity walls, and how to deal with them.

Fixing penetrating damp can be easy and cheap to do yourself. But, before you can treat it or decide whether to get a professional in, You'll need to identify the issue first.

Take a look at the gallery and read on below for a run down on what might be causing penetrating damp and how to fix it. 

It may also be that old bricks have become porous and are allowing water to get into your home. Either get these replaced, or paint them with an exterior silicone water-repellent fluid or limewash, that will allow walls to still breathe. This could also be a good preventative measure, too, but seek professional advice first on what would work best for your home's age and type.  

Clear wall cavities or add a damp-proof cavity tray

It is possible that penetrating damp is caused by problems with your cavity walls. Walls in modern homes (and many built since 1920) have a cavity between two walls, so that there is space for moisture penetrating through the exterior wall to evaporate before it gets to the inner wall. But there are a few reasons this could end up causing issues.

Where something 'interrupts' the wall, such as a window or pipework, you may have or need a cavity tray (see image below). These come in many different forms but effectively act as a way to drain any water away from the inner wall to the outside through 'weep' holes (holes in a part of the outer wall).

It may also be that old bricks have become porous and are allowing water to get into your home. Either get these replaced, or paint them with an exterior silicone water-repellent fluid or limewash, that will allow walls to still breathe. This could also be a good preventative measure, too, but seek professional advice first on what would work best for your home's age and type.  

Clear wall cavities or add a damp-proof cavity tray

It is possible that penetrating damp is caused by problems with your cavity walls. Walls in modern homes (and many built since 1920) have a cavity between two walls, so that there is space for moisture penetrating through the exterior wall to evaporate before it gets to the inner wall. But there are a few reasons this could end up causing issues.

Where something 'interrupts' the wall, such as a window or pipework, you may have or need a cavity tray (see image below). These come in many different forms but effectively act as a way to drain any water away from the inner wall to the outside through 'weep' holes (holes in a part of the outer wall).

If a cavity tray is defective, or there isn't one in place, these may need to be repaired or added - you can find out what the cost is of having a cavity tray added to your wall by visiting our damp costs page.

There are also reasons why your cavity itself might be causing damp. It may be that the cavity has become filled with objects, such as broken mortar or bits of brick, which are taking in moisture from the outer wall and passing it to the inner wall. In these cases, the debris will need to be cleared out to stop the issue (see our damp costs page for more details).

Lastly, in some rare cases, cavity wall insulation can cause damp problems. This is usually only the case if your home is exposed to severe levels of wind-driven rain or your walls are poorly constructed or in very bad condition. You can find out more in our guide to wall insulation and damp problems.

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