Roof Sheathing Orientation

Zip system roof sheathing general installation roof 60 panel orientation and edge spacing 60 taping 61 common details roof coverings 62 ice and water membranes 69 h clips 70 alternative details 71.

Roof sheathing orientation.

Structural sheathing panels have a strength axis that runs parallel with the panel s length unless marked otherwise. 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. 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. 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. Common roof sheathing applications and installation recommendations are described in the related publications listed at right. Roof sheathing is another matter since roofs experience forces applied both parallel and perpendicular to the long direction of the plywood. Why osb roof sheathing orientation matters.

Roof sheathing is a lot more than just flat panels onto which shingles are attached. The main one is the structure turning into a parallelogram where the studs are no longer perpendicular to the ground. 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. With 4x8 roof sheathing it will lay lengthwise perpendicular to the rafters trusses the grain is on the length axis.

For information on large panelized roof systems refer to the commercial construction application section. The following article was produced and published by the source linked to above who is solely responsible for its content. 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 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.

Journal of light construction december 11 1999.