We are attaching a new porch roof to our existing roof. How far up do we have to go up with the ice/snow/water shield beyond the point where the new roof meets the existing roof? We have two dormers right above where the new roof connects to the existing roof. Should we go up the sides of the dormers with the ice/snow/water shield also? If so, how far up? We live in New England with lots of snow each year.

I would have to see the exact conditions before I would attempt an answer.

At least three feet. What does the local township require? How steep is the roof your installing? What type of shingles are you using? You cannot over do the ice and water sheild. Although expensive. Its cheep insurance. But your best bet is to speak to the town on this. They can give you the best advice based on your area annual weather conditions.

Thank you for your responses. We attached the porch roof to the existing cape style home roof. We don't know the exact pitch but it isn't that steep. The top of the porch roof is about 1 foot below the front dormers. We have asphalt architectural shingles. We will be checking with our local Building Inspector for advice as well.