Shed roof and cladding - standing seam purlin/furring controversy
I'm planning a 7x3m posh shed (sauna and garden room) for a UK garden and have been looking at cladding and I'm lokomg the look (and honestly the cost) of cladco standing seam stuff compared to other attractive cladding options. Their install guides and videos have the sheeting going directly into 18mm OSB with a vapour layer between. That sounds great, nice and simple a roof I can crawl in for maintenance and being direct on the sheeting will stop it from banging like a drum in the rain.
Thing is, common sense says metal is going to get wet underneath from condensation, and other manufacturers' guides seem to suggest that the OSB will get wet and rot through in moments.
So, purlins and furring strips, or not? FWIW, I'm planning a cold/ventilated roof.