How to build loft extension if neighbour has one?

[bajgal]

Hi All,
I'm hoping that some Mumsnet wisdom can help me us here! DH has posted this somewhere too, but I know how helpful the Mumsnet hive mind has been and so I'm hoping some of you might be able to help me again!
We'd like to build a rear dormer loft extension to our mid-terraced house.
Our neighbour on 1 side already has a loft extension built, which is shown in the 2 attached photos.
From the photo's, it looks like the cheek of their extension is built to what appears to be the middle of the parapet party wall. We obviously want to build the exterior of the cheek of our loft extension to the middle of the party wall line too and we had originally planned to build up the parapet party wall in brick, to separate our 2 extensions and to act as the cheek wall. We thought this would be possible as our neighbour had told us that their extension was set back from the parapet party wall - I've only found out today that this isn't the case, after visiting my neighbour and looking up as you can't see this detail from our garden. Lesson learnt, that I should see to believe!
I want to ask you whether it will it still be possible for us to build our loft extension to the middle of the parapet party wall and if so, how would we do this. Do you think we'll still be able to extend the parapet party wall upwards as we'd planned? We really don't want to have to set our extension back if we can avoid it. Thanks to y'all!

We have a lift conversion as you describe, we’re in a semi.
The edge of our extension is an extension of the party wall and if our neighbours wanted to do similar they can cut into the party wall and build directly onto our extension.
Does that make sense?

Thanks Witchonastick (love it!), it does make sense. Was your loft extension only built halfway over the parapet boundary wall as our neighbour's is? Thanks!

No, we extended the actual party wall, which is why they would be quite within their rights to use it if they wished to extend.

I’d imagine if your neighbours only built on half of it, you could do the same and join your extension to theirs?
You would need a party wall agreement between you in any case.

Hello. My boyfriend does loft conversions and explained that it's not possible to build it half way for some reason (he used technical terms) he said if you get a carpentry company to have a look then they'll give you all options anyway!

We had to leave 60cm between our dormer and the neighbours as they refused to let us join onto theirs and we didn’t have enough time to persue it. However we think this was the best for us in the long run. (They are a bit mad!!)