Hi, why am I getting damp on my internal walls?

[rosandjohn]

Hi, I have had an office built in my garden its just like a little house brick built insulated, pitched tiled roof. It was plastered and has electricity. However there is some grey/black stuff that looks like mildew appearing in the corners up and down the internal walls any suggestions so I can go armed back to the builder. thank-you

[The Builder]

......two magic words Ros.......heat and ventilation...........was it just recently built............it could be still drying out

[netibiza]

Does it have foundations and damp-proofing?

[wiltsman]

If it's not heated I would suggest getting a de-humidifier. It works for me in my unheated conservatory.

[rosandjohn]

thankyou, it was built during the 'summer'! so is probably drying out. I've cranked up the heating -guilt free. thank-you:-)