Flat Warm Roof with Side Pitch

[Ricardo Da Silva]

I would like to have a flat warm roof for our new extension but as the our house has a pitched roof am not sure how the abut the too as the exterior walls will be flush and so the large flat roof fascia, deck and insulation will cut awkwardly into the pitch roof and i am not sure it is even possible.

So i modeled a flat roof with an eave noggin arrangement to create a pitch all round and would like to some comments from anyone that may have done something similar and if it seems feasible before I get an engineer to review it (See attached drawings)

Alternatively if anyone has an example or advice of how the first option; with large fascia cutting in might work, I would be grateful.

Also could you advise on how much either option might cost to build ?

Thank you