I have a \\\'marley\\\' tiled roof. A dormer juts out. In the bedroom a damp patch has appeared about a foot back from the join of the dormer and roof. In the loft space there is no sign of water getting in. Outside the flat roof looks fine. However to my suprise I found this strange \\\'valley\\\' thing that goes right from the dormer to the ridge tiles, about an inch across.It has a corrugated piece of material underlapping the tiles, under that is roofing felt.Is this normal roofing work or the answer found by someone who could not make the tiles meet each other? Roof is about 10 years old. I cannot see how the rain is getting in but it is ONLY when it buckets down.I can only assume the \\\'gap\\\' has something to do with it.Could I just tile over this gap or even fill it in with sand and cement?thanks, I shall now try to figure out how to do piccys.!