Can you tell me the benefits of putting 25 year shingles, as opposed to 20 year shingles? This is for a new roof. Second, should the ice and water membrane cover the entire roof? You will be pleased to know that we are putting in a ridge vent in! The pitch of the roof rises 4' over a distance of 12'. Sorry I don't know how to calculate the numbers and everyone else is out.
Answer:
They cost more if you consider that a benefit. The most cost effective shingle is the 20-year product so that's what I use. Ice and water shield on a 4/12 slope need only go up 9" past the exterior wall but I would want tar paper from there on up to the baffled ridge vent.
