On Mon, 29 Dec 2003 19:23:37 +0000, {R} wrote:


I have been doing DIY for 40 years, I can do anything but plastering.
This summer I finished my third floor to ceiling wardrobe/cupboard.

I have lived in this 2 up 2 down terraced house, built 1894, for 30
years. Very little except the main joists is original.

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.

The wall has never been damp before and indeed the area under and to the
right of the window in the same wall is still totally dry.

The cupboard construction is as I have done before a floor to ceiling
frame of 2" x 2" designed to perfectly accommodate 3 pairs of doors from
B&Q a 6' one and on top a 3' one.

My wife said that she found the inside of the cupboard cold as the
winter came on and now it is very cold in there even though the room has
central heating.

So I conclude that.

1) I have a condensation problem or
2) I have a ventilation problem or both.

Is their an easy solution, I suspect not. I assume that I have to force
ventilate or heat the cupboard, this is not appealing.

{R}

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.

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.

You say that not much in the house is original. Have you fitted
double glazing and generally draughtproofed by any chance?
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.

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.

The Celotex web site especially has some good application notes on how
to use this material. It can be cut easily with a knife (an old bread
knife is good) or a saw. It's foil covered on both sides.

I think that what I would do is to fit pieces of Celotex in the back
of the cupboard, temporarily taping in place with masking tape.
Check that it has the desired effect, and if so do a more permanent
job. I would make a simple wooden frame at the back of the cupboard,
fit the Celotex inside it, sticking it to the wall and then fit a thin
panel of your choice over the top supported on the frame. Make sure
that you seal the edges of the Celotex before panelling over it to
prevent room air from reaching the cold wall behind. That would lead
to condensation, which you don't want.

I am pretty sure that this will resolve the problem, but otherwise
fitting small vents top and bottom might be necessary - I'd try
without first.

Depending on the size of the cupboard relative to the room - i.e. if
you have covered a fair amount of the wall with it, you may find that
the room feels warmer.

..andy

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