I have a very old roof where rainwater runs down two tiled flanks which (almost) meet in a central flat valley (gulley?). See the attached image (which is slightly rotated!).
There's a leak which is only evident during heavy rain. Water is pooling on the flat valley just above the leak. It is supposed to flow to a gutter at the other end of the house, and it does to a large extent - just not when the rain is particularly heavy.
The obvious repair is to replace the valley entirely, but someone suggested a cheaper option of fitting a new slightly inclined valley just above the original. It would probably only need to cover about half the length - the rest of the valley )not in pic) is draining OK.
Does anyone have any experience or advice about that?
Thanks in advance.