The sarking boards on my new slated roof of my garage are damp , but on one pitch only. The front pitch is bone dry but the rear pitch is wet to touch, with the roof trusses also damp on this elevation. No evident signs of slipped slates . If it was condensation would have expected both pitches to be damp , if it was a leak would have thought it would be confined to one patch. Breathable membrane has been laid under slates . One end gable is feeling damp as well . Block construction. Any ideas?