The picture just an example of a pitch roof over the existing flat roof.
I got away with just building regulations on my flat roof to a hip roof using 20 degree angle as it meets their requirements, if it's bigger or more than 15% volume of your property blah, blah, blah, then you will need planning permission which is straight forward depending on your local Building Control Office.
This is how I did mine which is known as Overlaid Hip with 2 gulleys on each side
There's many ways of doing pitch roof over flat depending on the layout of your roof. Mono pitch, hip roof etc
I got away with just building regulations on my flat roof to a hip roof using 20 degree angle as it meets their requirements, if it's bigger or more than 15% volume of your property blah, blah, blah, then you will need planning permission which is straight forward depending on your local Building Control Office.
This is how I did mine which is known as Overlaid Hip with 2 gulleys on each side
There's many ways of doing pitch roof over flat depending on the layout of your roof. Mono pitch, hip roof etc