I am having quotes from contractors on a new roof over my deck. All three have different methods to tie roof in. I would like to know if the shingles should be removed under the gable end and then what type of flashing should go into the valleys. One guy suggested a rubberized ice shield. Does this mean he lifts the existing shingles up and how far under should the shield go? Or should I demand they use normal rolled flashing? I worry about short cuts