Identical rear extensions on semi detached houses

[blup]

The neighbour has an existing ground floor rear extension built recently to (we assume) current build regulation standards. It abuts the side boundary i.e. the middle of the pair of semis.

If we get permission to build an identical extension i.e. up to the side boundary and same depth, could we rely on the existing neighbours wall for the purposes of insulation requirements etc. or would our side wall have to be built as if it were a stand alone external wall.

Thinking of saving space, not concerned with noise at this stage.

Thanks

Blup

 

[^woody^]

If the wall meets requirements for compartmentation and party wall specification, you sorted out ownership and boundary issues in the deeds, and got formal planning permission, yes.