JK wrote:

Got an exterior wall that gets damp. Sometimes it's damp, sometimes not.
The dampness is always in the first 18" above the skirting board. The wall
does not have a cavity and it's always cold. I suspect the dampness in
condensation rather than rising/penetrating, especially as sometimes it is
enough to run down and sit in a pool on the top of the skirting. Am I
right?


Hard to tell. May be both. Its unusual for condensation to be at lower
levels only, but it can be if the wall is not getting heat there for
some reason. When I have had condensation it has formed over all the
outside wall, not just at the base. The only time I had that was in a
kitchen where it was both steamy,. and the wall base was covered by
units allowing no circulation.


I'd suspect a bridged damp course frankly, or none, giving classic
rising damp/penetration.

Check outside and see if the soil is above DPC level, and remove if it is.


Even if no DPC exists, you can vastly reduce penetration by digging a
trench round the affceted area and filling with shingle, provided it is
not in an area that is lower than local ground so it just forms a pond :-)



John