Property advice: My attic flooring is wet. Why?

Moisture from condensation will undermine timbers and cause rot

Your eaves ventilation is designed to allow draft cross your attic, where air is drawn through at one side and enters on the opposite side. This ‘airing’ keeps moisture at bay. File picture

Dear Brigid

I have OSB boards (oriented strand board) in my attic for flooring. I notice that they are all wet underneath and have been for some time. My ceiling joists are also wet, above the insulation. I mentioned this to a pal who works in construction, and he said it could be warm air rising from downstairs through cracks/openings in my ceiling. Is he right? Is this something I should be worried about? Could it affect the ceiling joists? If the answer is yes, how can I address this issue?