Terrace roof above leak from decking

[Eddieob]

Hi

Our neighbours have a terrace above our kitchen. When it rains the walls on one side of the kitchen gets wet.

The side of the decking upstairs the water proofing has come away and need some advice on what to use to seal it
Or glue it back if that’s possible.
Highlighted in the photo attached.

One side of the decking I cannot see the water proofing and will need to remove some decking to check. It looks older not sure if there is anything quick and temporary we can do untill we get under the decking

Thank you

[wes56]

Your first pic shows what looks like lead flashing - the lead is turned into the bed joint as it should be - is this cover flashing at the upstand of a flat roof?
The first pic is blurred and difficult to see clearly.
The second pic shows what looks like some kind of membrane thats not been turned into a bed like the lead, or sealed to the wall - and now its detached from the wall?
Was the membrane ever sealed or "glued" to the brickwork?

You will definitely have to examine below the decking and determine the condition of the flat roofing below the deck.
How does water drain off the deck?

Can you post a photo showing the whole flat roof and decking?

[big-all]

just a thought
if this is a flying freehold would it not be up to them to sort it??
another thought should it exist in the first place as you need permission for a raised plarform above 300mm from ground level??
https://en.wikipedia.org/wiki/Flying_freehold