}On Mon, 29 Dec 2003 19:23:37 +0000, {R} wrote: [...] }>The new cupboard is very damp on the inside, soaking the wallpaper that }>was there before the cupboard. The cupboard is on the front wall of the }>SW facing house, 9" brick with a lathe and plaster finish. } }I think that you've done a good job, {R} but have made a very }effective cold cupboard. It's possible that there is some }penetrating damp through the brickwork, especially as the wall is SW }facing, although the clue is that there was no apparent damp there }before. Even so, I would do some obvious checks on the outside wall }- for example is there a rainwater pipe that might be leaking, gutter }overflowing, etc.? Could there be any crumbled brickwork? Worth a }check.
Yes I have done that, I am convinced that it is not any form of leak. I had one of those in the other corner of the room years ago and that was fixed by reslating the roof. I failed to mention that the dampness is very uniform over the whole of the inside of the outside wall.
}However, if the cupboard is damp more or less uniformly across the }back, then my money would be on condensation and lack of ventilation. }The problem is that the heat loss through a solid 9" brick wall is }quite substantial, so the action of building a cupboard has been }effectively to reduce heat reaching this space from the room. It }would be interesting to put a thermometer inside and see how much }cooler it is than the room - I'd bet a good 10 degrees C. You don't }say what you used to make the rest of the cupboard, but most of the }composite sheet materials are pretty reasonable insulators, so in }effect you are making a cool box next to the wall.
There isn't much of the rest of the cupboard, it is only 16" deep, being built around the doors, and in a corner means there is only doors and one end panel of thin pine T&G cladding.
}You say that not much in the house is original. Have you fitted }double glazing and generally draughtproofed by any chance?
Oh yes.
}If so, in the winter, you may have quite low ventilation in the house }in general, leading to relatively high humidity. All that it then }takes is a cold surface, and bingo. The air will certainly be }finding its way into the cupboard, and my bet is condensing on the }cold wall at the back.
Low ventilation? None is closer to the mark, I was extremely relieved that when I had the gas boiler replaced after 22 years service the installers insisted on better ventilation.
SWMBO has a permanently cold hands and feet, and has ensured over the years that there are no draughts at all. We even have a double entry cat flap. I went and bought a CO monitor as I am/was concerned about the ventilation. It is snug.
}Assuming you are satisfied that the outside wall is OK, then I think }the next step would be to insulate the back of the cupboard. To do }this, a good solution is polyisocyanurate foam, aka Celotex or }Kingspan. This comes in 2440x1220mm sheets from builder's merchants }in various thicknesses. 50mm is a very common one and readily }available. This would take the heat loss through the wall almost }down to modern house standards. Probably 25mm would be good enough }to achieve the desired effect if you can get it. Expect to pay }about £15 to £18 a sheet for it.
That is what I needed to know, thanks.
{R}