A metal roof that 'rains' on the inside on a cold morning isn't leaking - it's sweating. The underside of the cold steel deck is below the dew point of the warm air rising inside, so moisture condenses there and drips down onto everything below. It's one of the most common calls we hear about Alberta shops and outbuildings.
Why the roof deck is the worst spot
Heat rises, carrying moisture with it, straight to the coldest large surface in the building - the roof deck. With nothing between the warm air and the cold steel, condensation is guaranteed whenever the temperature gap is big enough, which in Alberta is most of the winter.
The fix: seal the deck
Closed-cell spray foam applied to the underside of the roof deck removes the cold condensing surface: the warm air now meets warm foam. It insulates, air-seals and vapour-controls in one pass, ending the drip permanently.
Related: metal building condensation and spray foam roofing. Get a quote.