Thanks
Frank
You could treat the wall with one of thoise wetaherseal things to stop
teh damp seeping out and paint oiver, but I am dubius of the effect of
having a sopping wet wall that may be exposed to frost..
How about painting it with a bitumen-based (black) paint, then covering
that with an exterior paint?
Just floating it as a suggestion to be shot down; I really don't know if
it would work (especially the bit about overpainting the bitumen paint)
David