Joints in Panel-Type Sheathing

(1)  Panel-type sheathing board shall be applied so that joints perpendicular to the roof ridge are staggered where,

    (a)   the sheathing is applied with the surface grain parallel to the roof ridge, and

    (b)   the thickness of the sheathing is such that the edges are required to be supported.

(2)  A gap of not less than 2 mm shall be left between sheets of plywood, OSB or waferboard.

Article Ontario Regulation 332/12 Building Code,   Information published by for educational purposes only.

When plywood or OSB is used for roof sheathing, sheets are laid with the face grain at right angles to the framing (Figure 97) and with the joints offset to obtain a good tie across the roof framing. Leave a 2 to 3 mm (1⁄8 ) gap between panels to prevent buckling should expansion in the sheathing occur.

Figure 97

Application of structural wood-panel roof sheathing

Source : Canada Mortgage and Housing Corporation (CMHC)