Permitted Development Rights for Hip roof

[Hazel Evans]

I intend to build a 2 storey 3m deep rear extension with a pitched roof to my house. I am confused as to what roof I can put on it, as the house has a dormer first floor and my extension will match that. Does the extended roof area fall within class B limitation of 50 cubic metres for a detached house? If it does, how do I calculate the increase, as the existing house only has habitable area in the roof?

 

[RichA]

Do you have a photo, plan, elevation? It might make it clearer.

My understanding, and in my case, the PD 2-storey extensions are not typically judged against class B; but your first floor/roof design may impact that.

 

[Leofric]

Whatever it is you could always apply for planning permission if necessary.