Loft Extension - when is planning not given

[LondonBuyer]

Hi everyone

I am currently considering how to improve my detached property - it is 3 floors and unfortunately the top floor despite being quite large floorspace wise has a quite awful layout. Due to the way the roof has been designed it is mostly low ceilings and small windows so feels very dark and cramped. Given its size it would need planning approval rather than being under permitted development.

My thinking is to complete a "loft extension" on it - given there are already stairs, a bathroom, etc in place really what it needs is some of the sloping roof / walls being taken out and being replaced by some sort of dormer(s) with lots of windows or some french doors in.

This is all at the back of the property which overlooks a 30m garden - behind which is the rear neighbors 40m garden.

My question is - am I safe to assume I can pull off my plan to raise the roof and stick in some windows (all within reason) or have people come across strict rules around extending the loft? I worry there may be a cap on cubic space as the upstairs would be quite large just given the rest of the property is of good size. If it helps the borough is Croydon.

Croydon seem to be approving anything and everything at the moment!

Seriously though, you need to check the Local Plan to see what hte policy on extensions is (it's on the website).

If you are actually raising the ridge height of the main roof, there may be an issue. If it's just dormers at the rear it should be OK as long as there is no impact on neighbours privacy/light etc. The French doors might be a problem if you are thinking about a balcony of some sort.

This is assuming you are not in a Conservation Area or a Listed Building of course.