The Ontario Building Code | Thickness or Rating

9.23.15.7. Thickness or Rating

(1) The thickness or rating of roof sheathing on a flat roof used as a walking deck shall conform to either Table 9.23.14.5.A. or Table 9.23.14.5.B. for subfloors.

(2) The thickness or rating of roof sheathing on a roof not used as a walking deck shall conform to either Table 9.23.15.7.A. or Table 9.23.15.7.B.

Table 9.23.15.7.A.
Thickness of Roof Sheathing

Forming Part of Sentence 9.23.15.7.(2)

Item	Column 1 Maximum Spacing of supports, mm	Column 2 Minimum Thickness, mm Plywood and OSB, O-2 Grade Edges supported	Column 3 Minimum Thickness, mm Plywood and OSB, O-2 Grade Edges Unsupported	Column 4 Minimum Thickness, mm OSB, O-1 Grade and waferboard, R-1 Grade Edges supported	Column 5 Minimum Thickness, mm OSB, O-1 Grade and waferboard, R-1 Grade Edges Unsupported	Column 6 Minimum Thickness, mm Lumber
1.	305	7.5	7.5	9.5	9.5	17.0
2.	406	7.5	9.5	9.5	11.1	17.0
3.	610	9.5	12.5	11.1	12.7	19.0

Table 9.23.15.7.B.
Rating for Roof Sheathing When Applying CSA O325

Forming Part of Sentence 9.23.15.7.(2)

Item	Column 1 Maximum Spacing of supports, mm	Column 2 panel Mark - Edges supported	Column 3 panel Mark - Edges Unsupported
1.	406	2R16	1R16
2.	508	2R20	1R20
3.	610	2R24	1R24

(3) asphalt-coated or asphalt-impregnated fibreboard not less than 11.1 mm thick conforming to CAN/ulc-S706, "wood Fibre Thermal insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation for Buildings", is permitted to be used as a roof sheathing over supports spaced not more than 406 mm o.c., provided the roofing consists of,

(a) a continuous sheet of galvanized steel not less than 0.33 mm in thickness, or

(b) a continuous sheet of aluminum not less than 0.61 mm in thickness.

(4) All edges of sheathing described in Sentence (3) shall be supported by blocking or framing.

9.23.16. wall Sheathing