BTW. I realise that the damp might becoming from the upstairs flat, but no sign of damp there.
So hoping for a few hot days will dry balcony out, to prove source is rain.
I have a ground floor flat, Victorian house.
I have damp which seems to be coming from first floor balcony, from water puddling by a 4" waste pipe.
I'm on good terms with neighbour. Just need to sort out cause and fix it amicably between us.
History ; balcony was concrete, but few years back...