Penetrating Damp In The Home - Top Tips For Treating

Published: 12th January 2010
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What Causes Penetrating Damp?
The causes of penetrating damp in damp walls are ofent related to problems with the building or plumbing which has meant that unwanted water is entering the propert. Coastal propertiescan also suffer from penetrating damp due to the driving rain. This penetrating damp results in serious deteriorating affects to the internal finishing like damp staining, salting, blown plaster, spoiling and peeling of the finishes in the internal areas. A watermark might be noticeable on the internal wall and grow if the water continues to enter thus penetrating the damp walls.

Penetrating damp is caused by the porous nature of the building which permits external moisture to enter through the external walls which ultimately affects the internal surfaces. The defects in the construction of the building which are the root cause of penetrating damp include defective roof coverings, lead flashings, damaged mortar joints etc. Even when these defects can be cured, the affects of residual moisture within the building can continue to create problems for months and sometimes years.

This is so because a damp wall will take one month for each inch of the wall thickness to dry out after the source of the penetrating damp is removed.

Many older buildings have very very thick external walls and thus the affects of penetrating damp will continue over a longer period of time if nothing protective is done. Penetrating damp can also be a problem in damp cellars due to the soil from outside pushing against the brickwork. In below ground buildings a full damp tanking system would be recommended to treat the damp cellar.

As moisture evaporates from the wall, the chloride, nitrate and sulphate salts in the wall contain a nitrate in the internal plastered surface, where they manifest themselves and become 'hydroscopic' which means that they attract atmospheric moisture. Single brick walls are particularly prone to suffering from penetrating damp and in heavy rainfall it takes only approximately three quarters of an hour for an average brick to saturate, which means that they are almost always damp even if they appear dry or feel dry to the touch. If you have single leaf brick walls in a habitable area then damp proofing is inevitably needed. This is also common in areas where the dpc damp proof course is missing.

The correct identification of the cause of the damp whether it be rising damp, penetrating damp or condensation damp - is important and if it can be cured or removed then your are half way there. However, the residual moisture aspect must always be considered to completely remedy the problem.

DIY Damp Solutions

Numerous DIY damp remedies can help you treat penetrating damp. The first thing you should do is check everything in and around the property.

=>Check gutters, downpipes, rendering and window frames.
=>If you have any leaks, penetrating damp will present itself.
=>Look for cracks that water can enter through.
=>Blocked drains can also cause penetrating damp. Get rid of the blockage and the problem might fix itself.
=>Poorly fitted roof felt can lead to penetrating damp and damp plaster internally

Whether the penetrative damp is continuing or because of residual moisture, Damp Proof Membranes offer a quick and permanent solution for treating damp problems. Once they are installed, they provide a permanent separation barrier between the damp walls and internal finishes meaning a dry interior surface and protection is maintained always and the damp walls can dry out - meaning no more damp mould!. The recommended Damp Proof Membrane would have had a stud profile as it would stop penetrating damp. The stud acts as stilts holding areas of the membrane away from the surfaces to which they are applied and this maintains an air gap into which moisture and moisture vapour can evaporate and move without any hindrance. This in turn creates 'damp pressure equalisation' meaning the differing internal and external air pressures equalise across the wall. They effectively squeeze moisture which is in the air gap between the wall and membrane out of the structure. Also Damp Proof Membranes are totally impervious to the hygroscopic salts which are bi-products of the penetrating damp and associated residual moisture.

As a damp expert who has been dealing with treating penetrating damp for many years, I would always recommend Damp Proof Membranes as the solution for penetrating damp.


David Sutcliffe is an independent consultant specialising in the diagnosis of damp and penetrating damp in all buildings across the construction spectrum from historic and listed buildings to new build, commercial and domestic structures. David has over 30 years of hands on experience in installing damp proof membranes as well as having years of consultancy experience

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