I am having new dormer put on my semi detached house.On front it is going to have pvc cladding around window and on sides going to be slates.Also it is going to have new re roofing.Builders have re roofed around dormer as always new felt battens on it and slates over it.I have noted on side of dormer they have put felt and slates are nailed and screwed directly on ply wood.Are they not suppose to put battens on felt first and then nail slates on batons,are is it acceptable pratice.
