Roof Sheathing Orientation

Structurally it doesn t make a difference but if the grade stamp faces up it will be covered by the roofing material and the building inspector will not be able to confirm the right osb panel has been used for that application.

Roof sheathing orientation.

Structural sheathing panels have a strength axis that runs parallel with the panel s length unless marked otherwise. For information on large panelized roof systems refer to the commercial construction application section. We could in theory credit a plywood panel installed perpendicular to the rafters with the higher shear force in that one direction but we would be forced to accept the basic code value in the opposite direction. Common roof sheathing applications and installation recommendations are described in the related publications listed at right.

Journal of light construction december 11 1999. Roof sheathing is a lot more than just flat panels onto which shingles are attached. This solves two points of weakness. The osb roof panels should be installed with the grade stamp facing into the attic and the screened surface with the nail guide lines facing up.

Why osb roof sheathing orientation matters. With 4x8 roof sheathing it will lay lengthwise perpendicular to the rafters trusses the grain is on the length axis. The main one is the structure turning into a parallelogram where the studs are no longer perpendicular to the ground. On roofs and floors sheathing is installed perpendicular to supports because this is the orientation that results in the strongest roof or floor.

The roof s sheathing helps to keep the roof trusses or rafters properly spaced and is the strength that holds. Correct installation of roof sheathing will ensure the best performance and help reduce complaints and callbacks. If used for floor or roof sheathing where the primary purpose is to carry loads perpendicular to the face of the sheets then it must be placed with the long direction of the sheets perpendicular to the supporting joists or rafters. The same policy goes for roof sheathing as for hanging drywall you get more strength by spanning more rafters joists studs and offsetting the joints.

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