I have a problem with mould on a single skin wall in a bedroom.
It's a 1930's 3-bed semi with bay windows. Downstairs, in common with
the rest of the house, the lower part of the bay is cavity-wall
The problem is that upstairs, in the front bedroom, the lower part of
the bay is actually a 4-panel single-skin affair. Limited investigation
show that it's a wooden framework filled with a mixture of broken brick
and mortar, pebbledash-rendered on the outside and plastered on the
The inside surface of this bay gets quickly covered with large patches
of black mould. In winter, the surface is visibly damp.
I initially sealed the outside with waterproofer (Thompson's Rainseal or
similar) to ensure that no water was coming through from the outside
and then covered the inside with a double layer of 2mm polystyrene
sheeting to try prevent condensation.
Alas, in a few months, the PVA glue failed and the sheeting peeled away
from the wall because it was being lifted off by efflorescence. And, of
course, it is all now covered in mould again. :(
Is it possible to /ever/
treat a wall like this to prevent mould
occurring or should I simply do what I suspect is the 'proper thing' and
erect some kind of inner skin to turn it into a cavity wall?
If I do have to turn it into a cavity wall, what's the best material
(and method) to use?