How do I tie a new roof in to an existing roof with a pitch transition?
The new felt should go under the old felt.
The new flashing should go under the old felt and over the new felt and new roll roofing.
Depends on the slope of the new roof. The lower the slope the further it should extend.
Roofing nails to the existing structural sheathing.


The big idea is that layers of the lower roof should sit below corresponding layers of the upper roof. That is:


Everything should lap just like shingles.
Nothing should back-lap.
The flashing should double lap the roll roofing.
Even though the higher roof was installed first, the end result must be the same as if you started at the eave and worked all the way to the ridge.