Monthly Archives: February 2015


I’m often asked to investigate and remedy damp problems. Often this is not rising damp but it will be excess moisture within a house causing problems like black mould to appear on wallpaper etc.
My answer is always the same.
It is simple physics that the water content of moist air will readily condense back into liquid water droplets on any cold surface. This often used to be windows but not so often these days with double glazing, so the next coldest surface might well be a cold outer facing wall.
People say the wall is ‘damp causing the mould’ and I say no it is ‘coldness causing the damp causing the mould’
It doesn’t take a genius to figure you either have to make the wall warmer or get rid of the moist air. And since getting the wall to be warm will only make the moist air condense somewhere else it is the air you really need to get rid of.

Getting rid of the moist air:
Easy way
—ventilate or extract replacing the internal air with dryer air from elsewhere.
More difficult—remove the moisture from the air with a dehumidifier

The usual causes of the moist air:
A tumble dryer venting internally
Drying clothes on your radiators or elsewhere inside the house
A shower in a room without an extractor
Cooking done without an extractor
Blocked or absent air bricks
Never opening windows (permanently locked or unserviceable)
Breathing (I don’t suggest you try to stop)