Metal roof sheet

Hi, first post in here, after some guidance if possible. I’ve started building a low budget garden room, it doesn’t have to last forever so not spending silly money on one. The size is 3m x 6m (half of this space is just for storage) The walls are built from insulated cold room panels. I’ve got 4x2 roof joists at 600 centres.

Now the roof - I created the roof deck from old 18mm osb. I then wrapped in cheap breather membrane and have then fixed box profile metal sheets to the top. Left no air gap between membrane and metal. I know this is not usually a good idea due to condensation on the under side of the metal but the steel sheets are only 0.04mm thick, so flimsy as hell and didn’t want to fix onto battens (rattle in the wind) although I know that is the right way to do it. Do you think I can get away without an air gap for the size of the building?

 

As I read it the metal roof panels are on the outside on top of the roof, so any condensation would be outside the building and not inside. So I don’t see an issue

 

Thanks Jowwy, yeh metal panels are on the outside. Its box profile, so I’m hoping that any condensation or moisture rising from inside the building will be able to circulate out of the raised sections on the box profile and not collect under the metal. For this reason I have decided not to plug the ends of the box profile with foam so at least the air can flow up and down the raised parts.

 

That sounds ok.....but what about pests getting up under neath like flies, wasps, spiders and nesting under there?..

 

As long as they can’t get inside the room, I’m not too bothered tbh