On 10/05/2021 11:27, cf-leeds wrote:
It's a flat sloping roof with a single gutter across the back end of the garage - It's a prefab garage. (not a pitch roof).

I thought I'd just look online for some galvanised corrugated metal sheets, around the same dimensions at the old asbestos, but I find there are many products out there, including corrugated bitumen sheets.

I'm doing a similar thing. I think I'm going to use 3" corrugated
galvanised rather than plastic coated, on 11mm Sterling board. I don't
want bitumen or felt, might use EDPM but prefer corrugated.