I have had an extension built over the winter months. The builders fitted MDF skirting and soon after they fitted the skirting I noticed that mould was growing on the top and sides. The walls were dry prior to them fitting the skirting. I have cleaned them with domestos, caulked the joints and repainted with gloss but now after a couple of months it is all happening again. Can anyone sugest what i can do. I have central heating pipes running along the same wall below the skirting so do not think it should be damp. Would appreciate any suggstions.