Side extension - adding to current single story

[drb]

Hi to everyone.

 

I am looking to options to extend my current house (mainly to increase the upstairs footprint and increase the number of bedrooms), and am after any advice on the balance between this needing planning permission, or falling under permitted development. Ive attached a couple of quick block drawings to show the house (and the houses to either side). At present there are 4 houses (semi detached, with the party wall in the middle), 2 floors in one half, and then a single floor on the other (blue in the drawings), and the proposed extension in orange.

Ive also attached a floor plan, with the blue sections being the house, and the orange being changes previously made (at the bottom an internal garage conversion, and at the rear a 3*3.5 extension). 

 

In terms of work i am looking at, i would look to add a 2nd story above the current single, running the full length of the current rooms. I dont plan on going further forward, backwards or outwards. Currently the single story has a flat roof, and i would propose to retain a flat roof on the extension. 

 

I do have a short session booked with the duty planning person, but thats not for a couple of months (they are quite booked!). 

 

Any comments, guidance etc on the plan, and which path its likely to fall under would be appreciated. Any questions please ask - im happy to clarify.