Internal water stains on top edge of ceiling from parapet wall

Hi, first of all how do you know for sure that the parapet wall is the problem please? 1) It could be a Lead soaker is slipped causing a gap between the brick work of the parapet and the roof covering. 2) On a older type of property it could be the Lead soakers are made of Zinc and over a long period of time ie; 80 years or older these type of soakers become brittle and split. 3) It could also be just a Slate or Tile is missing. (Oh does your neighbours side leak also?) 4) If the coping stones over the years have failed now, you should when replacing them make sure there is a overhang over the existing brick work of around 2 inches your side and the neighbours side of the brick work. This is the correct way to replace them as there should never be any need to grind the brickwork off! Please try to look through a roof window if you or your neighbour have one or another good way is to look through some decent binoculars and try and identify the problem yourself. There is a lot of other options you can do but in my experience Lead has been proven over and over again provided it is cut in the recommended lengths and thicknesses. Without seeing some close up pictures of the job I can only guess the problem you have. You could post some here on My Builder then I would be able to tell you more. Hope this helps you and if you need anymore info on this problem just ask, it's no problem! Good luck Mr Keith Cooper For ROOFco