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Causes of Damp in Buildings

Maintaining a property might be a necessity, but it can also feel like a constant, niggling pain. Speaking of which, damp is one of the biggest headaches of all.
Unwanted but just about inevitable – damp is, simply put, unwanted moisture. It can lead to rot, plaster can deteriorate and wallpaper can blister and loosen. The growth of mildew and mould is unsightly and can allow bacteria and fungi to flourish – even causing respiratory problems such as Asthma. And if, say, floor timbers are affected, damp might also cause structural problems.
All of this might lead to a vision of some poor, afflicted ‘house from hell’ but damp does not discriminate. Every building is prone, because there is (just about) no escaping the causes.
Invariably there are three of them:


This is a 100 per cent certainty – since living in a house implies (we certainly hope) that you are breathing in it as well. That creates moisture, as do everyday actions such as cooking, bathing, washing and drying clothes.
Therefore, the air gets wetter and when it can’t hold any more moisture, water will gather on cold surfaces such as windows, tiles and walls.
The colder the room, the worse the potential problem. Yet simple steps can help prevent it from taking hold:

    • When cooking always use pan lids and open a window to ventilate the kitchen
  • When drying clothes, try and do it outside. If you live in a flat, or it’s pouring down, use a clothes horse in a room that’s cool (but not cold)
  • Don’t dry clothes on radiators: this is one of the main causes of condensation and can cause mould growth on wallpaper and soft furnishings
  • If you use a tumble dryer, and if it isn’t self-condensing, make sure it is vented
  • When bathing, run the cold tap before the hot; this will reduce the amount of steam produced. It’s also much safer, particularly if you have small children
  • Open the window a little to reduce moisture in the room
  • After bathing or showering, wipe down the tiles to remove the surface water. Then open the window and shut the door
  • Extractor fans, fitted in either the kitchen or bathroom, must be used properly – in other words, close all windows and doors. This will remove moisture more effectively
  • A temptation might be to switch the heating off to save money. However, heating set at a moderate temperature tends to be more cost-effective in the long run – while also guarding against condensation
  • Always keep your house ventilated, even in winter time. Prevent the blocking of airbricks e.g. by outside decking
  • Try not to place furniture against walls – particularly outside walls, as this prevents air from moving freely and also traps moisture

Penetrating Damp from Rain

Besides problems with roofing, such as cracked or missing tiles, the main cause of rain penetration is defective masonry:
Here is a list of some of the problems…

  • Blocked & overflowing gutters
  • Broken, leaking downpipes
  • Running overflows from cisterns and tanks
  • Porous masonry (under-fired bricks, porous stone, porous mortar)
  • Cracks
  • Defective pointing
  • Unfilled joints and prepends
  • Defective seals around doors and windows
  • Holes in walls – e.g. where cables or pipes protrude
  • Defective render

Properties must be properly maintained, especially the older ones.  It will be cheaper, in the long run, to maintain your property rather than repair the damage caused.

Rising damp

An age-old and ubiquitous problem, rising damp is the common term for the slow upward movement of groundwater in the lower sections of walls by a process called the capillary action.
It could be that poor drainage is a contributory factor, so for starters, it’s certainly worth checking for standing water in crawlspaces and basements.
An electronic moisture meter might be used to help the diagnosis, but rising damp can also be identified by a characteristic “tide mark” on the lower section of affected walls.  An experienced surveyor will use a combination of factors to diagnose the problem.
The tide mark is caused by soluble salts contained in the groundwater, which evaporates but leaves the tell-tale mark at the “peak” of the rising damp.  These salts are often chloride and nitrate.  They are hygroscopic and will attract water from the atmosphere.The control of salts is a very important part of damp treatments.
Damp can be halted by the presence of a damp-proof course – which is usually installed in walls to prevent groundwater rising into masonry.
In the UK, well-built modern houses include damp proofing in the form of a synthetic damp-proof course (DPC), about 15 cm above ground level, to act as a barrier through which water cannot pass.
However, a damp-proof course can be broken or incomplete, allowing moisture to cross the ‘bridge’.
Of course, the better the damp-proofing present, the less chance there is of rising damp developing. But just a few millimetres of ‘bridging’ is sufficient to cause it.
As mentioned, fighting damp is an ongoing battle. Something that cannot be understated, however, is the competence and experience of the person(s) undertaking the investigations: misdiagnosis does happen – and the costs can be high since the wrong form of treatment could be prescribed.
Please contact us if you have any queries – whether it’s about damp proofing or any of the other building services Danford, Brewer and Ives offers, such as timber treatment, condensation control, basement conversions, extensions or building maintenance.
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