Damp patches in dot &dab

[DaveOC]

Hi
I've had a new extension built, the builders have put dot & dab board all round, on one board damp circles have appeared this is from floor to ceiling (only half the board is affected). The wall which was an outside wall but now inside, is caverty brick and was built in the 1980s. the property is a bunglow and is dry above the wall in the loft.
Can't be rising damp as it gose to ceiling which is 9 feet high. Has any one any idears what is causing this.
Thanks Hope it makes sence

 

[rdw exteriors]

has it been skimmed yet? is the board damp?

 

[DaveOC]

Yes, it has been skimmed for about two months, Also the damp patches get bigger then smaller this does not seem to be weather related eg nice dry spell damp is bad.

 

[nwhessian]

There aint no pipes etc behind there? And its not leaking from above down?