45 degree rule for rear extension - planning

[David WE Roberts]

I am currently reading the Haynes Home Extension Manual which is surprisingly readable and covers much of what I have been struggling to research from various other books.

Howeve in the 'Planning & Building Regs' chapter it talks about 'right to light' and the 45 degree rule - a line at 45 degrees to the corner of your extension should not cover a neighbour's window.

Now we live in a semi, and all have a rear 'outcrop' which originally held an outside toilet and coal shed. This complies with the 45 degree rule. In many houses (ours included) this has been converted into a kitchen extension by knocking out part of the back wall of the house.

Several of the semis on our side of the street (where we can see the back gardens) have built all the way across the back of the house; extending this 'outcrop' sideways. This seems to conflict with the 45 degree rule as when you build up to the boundary you must cast a shadow across the rear of your neighbour's house.

So:

(1) Is this 45 degree rule recent? I can think of loads of extensions where this has not been followed. (2) Does it perhaps only apply to two storey extensions? (3) Is there another rule which 'trumps' this such as one allowing full width extension for a certain distance behind the house?

Oh, and is there another forum I should consult such as 'uk.rec.legal.moderated'?

TIA

Dave R

[Tinkerer]

I heard about a 45 degree rule recently when my son-in-law was planning an extension. Curiously this applied not horizontally but vertically. They were told that, in the case of a side extension, it should be possible to run a 45 degree line up from the window cill of a neighbours house without impinging on the new extension. I can think of numerous places where I have seen extensions that do not follow that rule as well.