I have a steep pitched shingle roof that has had a leak on and off now for 20+ years right in the valey between the main roof and my dormer. I must of had 3 or 4 contracvtors out to look at it and try to fix it. It was only when I called GF Sprague and got them to take a look that the leak was stopped. Bob, told me all about how the winter ice gets under the roofing and "creeps" (or something like that) up the roof valley. They went ahead and installed an ice dam preventer. Bob was great and very communicative; I knew almost more thna I needed to about what was going on, and why GF Sprague was doing what they do. All in all, I truly recommend GF Sprague.