Increasing previous extension- permitted development or planning permission?

[squeakydog]

I've tried to google this but can't seem to figure it out- if anyone more au fait with the rules than me could advise that would be great.

Just moved house, it's detached. Previous owners did a single storey extension, I think about 4 metres out, but just across half of the back of the house.

Are we able to 'complete' the extension, so essentially square the house off within permitted development? And can we potentially add a second storey if we only go out 3m and ensure all other requirements are met re windows etc?

Garden is about 100ft long so no issues with being close to end of garden.

I'm trying to work out whether you only get one extension within permitted development even if you don't max out what you can do basically.

Likely that you can square off, as you can extend from the original dwelling house wall... 2nd storey no

@Goodebe even if a second storey was within permitted development rules the if the whole thing was done from scratch now? Ie no initial extension ever done?

If you are adding a double storey extension, it can’t be taller than the highest part of your existing roof; mustn't extend beyond the rear wall by more than 3m; must be at least 7m from the boundary; be built in materials to match the original structure; no two storey extensions can be made to the front of the house, or to any wall parallel to the highway. So you may be ok!!

We are in the middle of building an extension to "square off" an existing wraparound extension. We ended up having to go through planning as the area of all extensions (existing and proposed) were greater than half the footprint of the original house, even though the bit we were adding on was quite small.

@RestorationInsanity is it a double storey? Is it just the square footage rule that meant planning or anything else that required it too? I'm fairly sure we should be ok on the size rule.

I understood it to be that the entirety of the finished extension is what is taken into account for the decision whether it is permitted development or needs planning permission. Give the council a call, they're usually pretty helpful

No it's single storey. Permitted development allows you to build multiple things, as long as individually or cumulatively they don't exceed/contravene any of the permitted development rules. So for example if you do a loft conversion, and then have another bit of loft you want to convert, you can, but both together must not exceed the volume limits for permitted development. Agree with @CloudPop, if you are submitting plans etc yourself rather than using an architect (who would be able to tell you whether it will fall under permitted development), then best to call the council.