Roof structure for garage with formwork or underlay membrane?

Hello everyone,

the roof structure of our garage is upcoming.

It will be a shed roof with a 15-degree slope towards the back. The roofing will be trapezoidal sheet metal in order to install a photovoltaic system later.

The garage will be unheated and therefore we do not need any insulation, which makes no sense anyway with 24 cm hollow block as the exterior wall.

Should the roof structure be executed with a solid sheathing and sealing with a bitumen membrane? Alternatively, a vapor-permeable underlay membrane was suggested to us, with battens and counter-battens on top as well as the sheet metal.

What do you think is the best option? What should be used in terms of the photovoltaic system?

Thank you very much for the help

First waterproofing membrane and then sheet metal again? The double waterproofing membrane would already be enough! I usually know the combination the other way around for hall roofs: sheet metal, vapor barrier including separation layer, insulation, double waterproofing membrane.

I would tend to USB and sheet metal purely from the simple execution. If the sheet metal leaks at some point, you can quickly see it this way as well. However, sheet metal is very loud and tends to form condensation underneath very quickly depending on the emerging room climate.

Which looks nicer as it ages (sheet metal or cardboard) is probably very subjective. Neither is really nice anymore after a while...

From the gut, I was thinking of the roof truss, underlay membrane, battens, and metal sheet.

Would that be okay?

Are there any issues with airtightness?