Common flat roof junction detail - part wall query

The rear bedroom in my semi-detached house has a dormer (same as all other houses in the street). This dormer which has a flat roof is attached to my neighbour's dormer so the flat roof is shared although I am not sure if there is a break at the line of junction (image attached)

I am changing the felt and replacing with fiberglass as part of other work we are doing and as part of the party wall discussions, the neighbour has asked for the "junction detail" of how we plan to safeguard their flat felt roof when we do ours.

My architect is out of the country so of no help for a few weeks and as I want to get the party award in place, wondering if there is a standard way to do this to satisfy the neighbours that I myself can specify with a simple drawing?

Googling, I see that we may need to put a small parapet wall and use lead flashing to fix the neighbours side quite easily but I can't see anyone having does this in the area so wondering if there is some other standard way to do this.

Any pointer will be very helpful to get the party wall settled

The Party Wall Act does not apply to roofs

^woody^ said:

The Party Wall Act does not apply to roofs

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Thats very helpful. Thanks.

Frustratingly, it's my own surveyor (who also acts for the neighbour) who asked for this. He actually knows the neighbour personally for several years so maybe biased

I will ask him to clarify if this is a party wall matter. There is no parapet/party wall going above the felt roof so as you say, it's purely a roof matter and hence not part of the PWA

Is he a proper surveyor?

^woody^ said:

Is he a proper surveyor?

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Yes he is proper and has credentials etc. Locally well known but in this particular case, I realised too late that he is family friends with my neighbours. No wonder my neighbours immediately approved my recommendation to go with him. In anycase, if I had chosen someone else, they would have still wanted him as their own surveyor I guess - so not escaping it
On a related topic he has asked us to excavate our foundations using a "hit and miss" method as my neighbour's conservatory is adjoining my planned extension. Its about 40cm away from my excavation. Its a 3m length that we need to "hit and miss" so its not so bad I guess but still wondering if this is a common process for excavations next to adjoining structures.

What are you actually doing? It sounds like you have instructed this surveyor for some reason, but your post only mentions roof work.

If the PWA does not apply he should not have accepted any instruction for that. If its non-PW work then yes he can take instruction, but he can be just as easily un-instructed.

You can use a length of mop roll on the dividing line so his felt can lap up this, and so can your fibre glass. You can then cover this with a lead cap to weather the joint.