the builders amended dormer roof to keep below top of ridge tiles. they trimmed the firrings and will direct water under the ridge tiles and on to front roof. I've attached a couple of crude not to scale diagrams and a picture. I hope they can tidy it up a bit, doesn't look so neat now. The felt is 3 layers torched on. Never heard of this method before, I wondered if this is a good way of keeping a roof water tight?
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I think that's a recipie for disaster.
Just looking at the 3rd pic, of the dormer cheek.
Don't want to pour cold water on it but I suggest it could have been done a little better. The capping on the fascia is not right; they seem to have missed a course of tiles at the top on the front, and the junction between the cheek and the existing roof looks suspect. Have they just mortared or mastic'd it up?
These things make one wonder what else might not be right. But it's the ridge tiles that are patently wrong and the main problem. Perhaps you should have left them as they were, even if they were a touch higher?