New GAF Systems Plus Warranty roof in Millbrook, AL. The back porch roof was structurally comprised so we added a layer of 1/2" OSB (oriented strand board) plywood over the existing substrate. In the 70' s and 80's the predominant type of plywood used on houses and/or additions was 3/8" CDX plywood. While 3/8" plywood passes code in none coastal areas, it causes the roof to sag over time. By adding a layer of 1/2" plywood we eliminated any low spots in the roof. We then installed synthetic felt underlayment and GAF Timberline HD shingles to the entire roof.
Billy Guyette - Montgomery native, roofing specialist