Party wall - is my neighbour's ask reasonable?

[fancyyang]

Hi i am planning a side return extension and am going through the party wall process. The neighbour's surveyor has suggested below:

The rainwater gutter drainage will have to be diverted on to the side of your property into new suitable drainage arrangements to carry loads from both the properties. Please provide details.

Is this request normal and reasonable? If not, what's the standard practice? Why should I build sth that would take loads from both my property and the neighbour's? Or do I have any choice at all? Thank you in advance!

What happens to rainwater now? Our semi has guttering that covers both properties and two downpipes - so wouldn’t be an unreasonable request for our neighbours the

At the moment we each have separate rainwater gutter drainage. I get that he doesnt want his drainage to be impacted from my work but cant understand whether it can justify asking me to find a solution that also carries loads from his property? Does it mean i would effectively maintain the rainwater drainage for him forever?

You should have your own surveyor answering these kind of questions. Who did you appoint in the party wall notice?

My survoyer is very bad and rude. He dodges my questions just say as i start the work i need to pay. The sad thing is that i cant get rid of him easily... hence i am seeking some advice here. I just want to know if it is usual practice to ask me to build sth that also carries loads from the neighbour's property? If no then what is it? Thank you.

your b=neighbour could quite legally ask for an independent surveyor for which you would have to pay - is it worth it? having good relations with neighbour is very important ...

mistype honestly no b= (is it Freudian slip??? :) )

Do you have a builder yet? We are near the end of our extension/reno and our builders are very knowledgeable on all aspect including compliance stuff.

@fruitbrewhaha, i dont have a builder yet and would love to talk to yours if you dont mind. Do you mind messaging me the contact? I live in south west london btw.