Rising Damp

 by: Alastair Taylor

It doesn’t sound like a particularly interesting topic, however a quick search on the worlds favourite internet search engine will show that in some circles rising damp is a very hot topic indeed. The trouble is that it appears that it could indeed be some type of religion or god; does it exist, or doesn’t it? The truth of the matter is that rising damp does indeed exist in one form or another, but it is often misdiagnosed, or you can often pay for expensive treatment that really isn’t necessary.

Rising damp in buildings may be defined as the vertical flow of water up through a permeable wall structure, the water being derived from ground water. The water rises through the pores (capillaries) in the masonary by a process loosely termed "capillarity." In other words the masonry acts like a wick The common causes are deterioration due to age and bridging of a damp course with internal concrete floors, renders or external paths and earth levels (a damp course is specifically designed to avoid the possibility of rising damp- it is built of a matter of course in all new buildings).

If your house does have a problem (something we will discuss later) then it can cause the following symptons:

For inside walls

• Paint does not adhere to the wall.

• Wall paper lifts and stains appear on the walls.

• Plaster flakes away, feels soft and spongy, bubbles and white powder or crystals appear.

• Skirting boards and floor boards rot.

For outside walls

• Mortar frets and falls out between bricks and stonework.

• Stains or white powder appear on walls.

These problems are mainly aesthetic problems only, however it is conceivable that structural damage could result from extensive rising damp, and of course a damp mouldy environment could pose a health risk to people.

Obviously if you have any of the above symptoms then it is possible that your home is suffering from rising damp, and it would be advisable to get an ‘expert’ in to look at your home. However this is where you will face a major problem; who is an expert , and who is just a ‘cowboy’ out to diagnose you with the "worst case of rising damp that he has ever seen, which can only be solved with the most expensive treatment on the market"? Unfortunately there are a lot of companies out there who have targets to meet and profits to make, and the way they do this is by over zealous diagnosing, and charge you hefty fees for carrying out work that may, or may not, fix the problem.

The major problem is that any damp-proofing salesman that you employ to look at your home will use a ‘rising damp meter’. These meters are supposed to measure the moisture in materials, however what they actually do is measure the electrical conductance. The idea being that the better the conductance (the ease at which electricity flows) the higher the water content. However these meters can only be calibrated for one material, and that is usually timber. So they will give reasonable results for wood and possibly some plasters, but for bricks, wallpaper and concrete they will give readings that are way too high. Thus they can be used (by unscrupulous salespeople) to indicate that you have rising damp “because the meters says so” when in fact you have a perfectly normal wall.

In summary if you can visibly see a problem with your wall, with obvious signs of damage due to water or salty tide marks then you may have a problem with rising damp, and you will need to try to find a reliable expert to come in and look at your problem. However be very, very wary of any ‘expert’ who has been employed to do a general survey of your house, or indeed comes around offering a free check up of your building. If they pull out one of these moisture meters, jab it into the wall a few times and declare that you have a major problem, then it is entirely possible that they are a commission based salesperson trying to extract money from you.

Generally, if the wall looks okay, it is okay. If it looks like it is damp, mouldy or has tide marks on it, then you have a problem with moisture, condensation, or rising damp in your home, and you need to investigate things further.