Good morning, everyone,
I have finally completed adding barn roof addition to the main house stucture. The new roof is 15-degrees in slope (approx. 3.2/12), which attaches to main roof that is 30-degrees (6.5/12). The transition is pretty mild in general. The 3/12 roof has double layer of OC Deck Defense. I was planning to place Grace Ice and Water shield on roof transition and overlap bottom portion into double deck defense. I was also going to leave maybe a 3-4 inch bottom piece to actually lap over the layer of shingles (should the transition ever leak - it would move water back onto shingles instead of remaining between shingles and underlayment. I was going to have continuous shingles through transition. Since the angle change is small, I do not think they will crack overtime.
However, the home inspector recommends using metal to flash transition. This means I will have break in continuity of shingles. What I envision is continuing shingles up to and even slightly over the transition, then nail the metal flashing that will overlap a layer of shingles on 3/12 roof and go up a few inches on 6/12 roof. Then start new row of shingles with bottom edge butting up to transition bend. This may be less pretty than continuous shingles, but I do agree that it will probably be longer lasting.
What do you all think? Would Grace IWC work just as well as metal flashing? Would you suggest one or the other? And would you change anything from what I described to make it more watertight?
Thank you all for your help!