The Norbord team offers some solutions for a telegraphing issue that one of their clients is having with their roof that appears on the horizontal 8′ panel edges (sometimes running the length of the roof).
This issue seemed to be installation related. The proper panel installations calls for fasteners to be placed 3/8″ of an inch from panel edges and this also holds true for the intermediate trusses. Their installers are positioning fasteners between 2″ to 4″ from the panel edges (on the intermediate framing members). This mis-application is allowing the 8′ edge to lift slightly creating a horizontal telegraph line on the roof. The telegraphing is accentuated by the angle of the sun that cast shadows on the roof. On a flat roof with an 1/8″ variation of the roof deck it will cast a very visible shadow. We also found a number of other issue. They are using #3 lumber for their trusses, plenty of wane, knots and twist. This lower grade lumber also opens the door for more uneven surfaces that ultimately effect the flatness of the roof area. There were also a number of shiners (fasteners that missed framing).