Building against the party wall

[Norm83]

Hi, I am planning a first floor timber extension over my existing ground floor cavity masonry extension. I have noticed that the neighbours first floor extension has been built so that their outer brick skin is over the party/ bounday line. The cavity of their wall is over the party wall line. With regards to my new extension, am I able to use their wall and build off of it seeing as it on my land or will I be forced to build inbound and leave a ventialtion gap. I obviously want to maximise the space in my new build. Is there a standard construction detail in this tye of sitatution. Some photos attached. Thanks in advance for any feedback

 

[PartyWallAgreement]

Sounds like a tricky one. Have you had a chat with your neighbour about how their wall sits over the boundary? Just wondering if they’ve run into any issues with it since they built theirs.

 

[PartyWallAgreement]

Just to add - you might find it useful to look into the party wall side of things before making any decisions. I came across this party wall site which explains the rules in a straightforwad way. Could save you a headache later on - let me know if I can help.

 

[PartyWallAgreement]

That sounds like a nightmare, sorry you’re dealing with it. Shared gullies always seem to cause more headaches than expected. Did you need to involve a party wall surveyor when it was first repaired, or is that only if structural work is needed? Curious what others here have done.