Dampness or condensation?

We residential Chartered Surveyors see fewer cases of rising dampness than was the case 20 years ago, whether a testimony to the success of the timber and damp industry in tackling the issue, or the introduction of modern materials which prevent its transmission to the internal surfaces of the building. However alongside this has come the exponential growth in condensation issues affecting buildings, and which is most prevalent in the winter months.

I have recently been asked by a client to inspect a building with a suspected roof leak apparently resulting in high levels of dampness and mould growth in a fitted wardrobe. His contractor carried out the necessary investigation and eventually found perished roofing felt which seemed the likely cause, carrying out repairs at a cost of several hundred pounds.

The odd thing was that the dampness did not appear during or immediately after winter rainfall, but a couple of days later. Further enquiry suggested this to be during a dry and cold period. On inspection it was found that that the wardrobe was both unlined and lay in a north corner of the building. This represents a typical combination of circumstances which give rise to condensation, as was the case in this instance.

In another case, clients had re-roofed and couldn’t understand why moisture was dripping from the roof and rafters were damp. The likely problem was that high levels of condensation were rising through the fabric of the building, leading to the air cooling in the insulated void in cold winter conditions and condensing to the underside of the roof tiles.  I was able to introduce a reputable damp specialist to advise on condensation avoidance and management.

The rise of condensation problems in buildings is due to a number of factors, including:

  • building changes – the loss of naturally venting chimney flues and fireplaces
  • bathing and showering practice – a generation ago showers, if fitted, used a fraction of the water of a bath. Now they are universal whilst modern mains pressure or electric power showers introduce water volumes which may be comparable to a bath
  • lifestyle changes – in the case of working families there is simply no time to introduce adequate levels of natural ventilation by throwing open the windows in the morning

So what can be done? A few simple measures may help:

  • open windows in the morning if you are able to remove overnight respired (and perspired) air, and moisture arising from cooking and showering. If not leave windows on trickle ventilation.
  • operate central heating at a consistent low temperature rather than turning it off when the house is unoccupied (the colder the temperature the less moisture the air can hold and the more likely it is that moisture held will condense).
  • beware portable infrared heaters which provide comfort to the body without heating the air in the room, so allowing air temperatures to drop to low levels.

Remember, condensation which leads to black spot mould is potentially damaging to the health of building occupants and should be addressed urgently.  If you are concerned speak to a Chartered Surveyor or reputable damp specialist and member of a recognised trade body.