Should I build a low-Pitched roof single story rear extension (14 degrees) versus double pitched with a Gully. There are advantages and disadvantages to both. I have an existing single story rear extension with a pitched roof, and I can add another next to this with a gully in-between, or I can take the pitched roof off the existing extension and put a low-pitched roof to cover the existing extension and the new extension( aesthetically this may look better) I believe the 2 pitched roofs would be a cheaper option, because I already have a pitched roof in place. I have heard there maybe drainage issues with a gully, but there are drainage issues with a low-pitched roof too. It is north facing and I don't live in a coastal area. There are tiles designed for this low degree roof profile which I could use. I also want to fit 2 roof lights (Velux) as well.
These are the 3 possible designs, but not sure whether I can have triple sliding doors, in terms of internal roof support, as the internal area is an open space. Any advice please?
in terms of costs, I would have thought it would be less expensive to build an adjacent pitched roof, than remove a pitched roof and replace the whole extension with a low pitched roof with specialist tiles from Sandtoft for example. I have also read that to avoid leaks in the future with low pitched roofs, the builder should do the following steps
OSB
Torch on
cross batten
felted
Battened
Anyone with experience of using these low pitched roof tiles?