Extention to join Outbuilding to Main house

[SALL2009]

I have a general query and hope someone can give me a rough answer. I have a Semi detached house that has not been extended in the past. There is a toilet and a brick building (shed) in the garden. The distance between the out building and main house is less than 3 meters (so within the permitted development scope)
My question is, would I need planning permission if want an extension of 3 meter depth with full width of the main house and then combine the outbuilding within the new extension. So an “L” shapes extension. The house is not in a conservation area.
I want to knock the old outbuildings down and rebuild. Would something like this be within the scope of permitted development and would be achievable without planning permission?
I know I would have to consult a planning advisor before I go ahead, but just want some information from someone with more knowledge of planning Laws.

 

[^woody^]

This is one of the ambiguities created by the new PD rules.

If your proposed new extension would otherwise be PD, and the connection to the outbuildings would effectively create a single extension which would then exceed the PD criteria, then it would no longer be PD.

The key is generally in the terminology, in that the PD rules refer to the "enlargement, improvement or other alteration of a dwelling house" so in altering/improving the outhouse this makes it all be considered as one extension.

If you just build the extension and leave the outbuildings, then that would seem to be PD.

You will probably have to get a definitive view from your local council (not an agent), and if they can't give one, then either apply for formal permission or apply for a Certificate of Lawful Development