Building extension on someone else's extension

[jbalciunas]

Hi,
I have moved into a flat and noticed that my downstairs neighbor is building an extension. Once that's built, could I build an extension on it?
What permits would I need? I am in a share of freehold flat.

Thank you
Justas

Not unless they agree, which is unlikely unless the wall is across a shared boundary so partly on your side. If it's all on their side I can't see why they would agree.

I’m reading it that they are downstairs, not sideways?

I've just seen its downstairs. So, you want to build on too of their extension? Of course you can't.

Hi Justas, I think you need to consult the solicitor who undertook your conveyancing. My understanding istis that in a normal freehold all the owners are jointly responsible for maintenance etc. I would also expect all owners to have a say in anything that affects the structure and maintainability. An extension would surely be covered by this.

All deeds are different hence the suggestion to consult a solicitor, but I reckon you might (just might) be in with a shout. Either way I wouldn't hang around and you will need to ensure any footings ate strong enough to take a first floor.

Surely not .. they will probably have sky lights and stuff

You can only build on top if they’ve put stronger foundations in to be able to do this. And as a pp said they’ll have skylights surely.

You must have given permission for the extension if you have share if Freehold. The time to suggest building on top would have been when plans were put forward. If you've just bought then check they have Freeholders permission. Extensions increase building insurance so must be communally agreed.

They are extending to the side in front of my window.

Justas

I think we need a diagram. I can't picture this, but, if you are asking if you could build on top of their new extension, the time to have thought about it was when it was first mooted, so that the correct foundations could be put in (and, of course, if they were agreeable). What if they are planning on having large roof lights? I think this particular ship has sailed.

this is where it is now

and this

Of course you can't, unless 1) the foundations are suitable 2) you have PP and 3) freeholder consent. And that is ignoring all the issues around shared costs, windows etc.

The time to have inquired about this was when the downstairs flat owner requested freeholder consent for the extension.

The OP implies that they have only just moved in so may not have been consulted.

Foundations (footings) are normally built to take plenty.

Contact your solicitor, this should have turned up in the searches.

You need planning permission.
That's like saying my NDN has a extension so I can just get one too .

FYI you may not have been consulted anyway . When the council write to neighbours they are sent randomly so may not be NDN or in your case the flat above .

No you can’t just build on top of it. You’d need their written permission, plus their extension would have to be strong enough to support a second storey, plus you’d need planning permission.

I don’t see why they’d agree to let you build on top of their extension. It wouldn’t benefit them at all and would just cause them hassle.

It might benefit them in terms of less heatloss, and OP would be paying for some of the shared extension, so it may reduce the overall bill. You might not need planning, as this may come under permitted development if not too big an extension (I have no idea on this, you'd need to check)
Always worth enquiring.

as this may come under permitted development if not too big an extension

There is no PD for flats.

The extension will be getting built on their land/garden so no you can’t build on top of their extension. Plus it will probably have roof windows.

1. are you leasehold or part-freehold?