We just had a new roof installed using Certainteed Grand Manor shingles. Our house was built in '35, so this was a replacement for a deteriorating slate roof. When we went up into the attic, we noticed that many nails go well through the boards under the roof, in some cases more than two inches. However, this varies a lot, in some cases the nails do not go through at all. What is the standard for nail length? The effect of the nails poking through is that it is now a bit dangerous to walk up in our attic. I also worry, will this cause leaks? They used 30 pound paper.