TECHNICAL BULLETINSTRUCTURAL BOARD ASSOCIATION Representing the OSB Industry 25 Valleywood Drive, Unit 27, Markham, Ontario, Canada L3R 5L9 Tel: 905-475-1100 • Fax: 905-475-1101 • E-mail:
[email protected] • website: http://www.osbguide.com OSB (ORIENTED STRAND BOARD) AND THE CANADIAN BUILDING CODES The latest Building Code information of importance to specifiers, contractors and dealers. 1. OSB CONFORMING TO CSA O325 “Construction Sheathing” OSB may be used for subfloors, roof and wall sheathing in accordance with end uses and spans shown on the panel mark. The 1992 standard (re-affirmed by CSA in 2003) is a performance based standard for subfloors, roof and wall sheathing. Panels installed on framing are evaluated for their ability to carry loads, and resist deflection under loads and conditions simulating or exceeding those experienced in construction and service. CSA O325.0 Construction Sheathing panels may be of any thickness and of any wood based material, e.g. veneer, wafers, strands, etc., alone or in any combination. The components must be bonded with phenol formaldehyde resin or equivalent. The criteria is their ability to perform, not how they are made. The ability of a product to meet performance requirements of a given end use is shown on the panel by a PANEL MARK. This Panel Mark consists of an end use mark 1F, 2F, 1R, 2R and W and a span mark 16, 20, 24, 32, 40, 48. The “F”, “R” and “W” indicate respectively floor, roof and wall sheathing. The “1” identifies panels that used alone meet structural requirements for the end use. The “2” indicates panels that require an additional support element, e.g. 2F subfloor panels require an underlay, wood strip flooring, or concrete topping; 2R panels require edge clips or blocking. The two digit span marks derive from imperial/inch measurements of the span, e.g. 16 indicates a maximum span of 16 inch (400 mm). Panels may qualify for more than one end use, e.g. a panel may be marked 1R24/2F16/W24. Part 9 of the Building Code uses Panel Marks, not thickness, to show the minimum panels permitted for specific end uses and spans. Construction sheathing panels are marketed according to Panel Marks. Actual thickness, determined during qualification testing, is not required to be shown on the panel. For a given span mark, e.g. 1R24, it can vary slightly between manufacturers (a thin, strong, stiff panel may perform better than a thick, weaker, less stiff, panel). However the nominal thickness can appear on the grade stamp, as per the following table. Nominal Thickness (mm) 7.5 15.0 9.5 15.5 11.0 18.0 12.0 18.5 12.5 22.0 CSA O325.0 OSB Construction Sheathing is available from SBA members. The minimum nominal thickness shown on the panel mark can be 0.5mm less than the values shown above. For building code purposes, the table below shows some equivalent strength thicknesses. Building Code 12.5 mm 15.5 mm 18.5 mm 12 mm, 15/32, 1/2 15 mm, 19/32, 5/8 18 mm, 23/32, 3/4 Panel Marks 2. OSB CONFORMING TO CSA O437 OSB GRADE O-2 may be used thickness for thickness on the same spans as plywood. The 1993 CSA standard O437.0 “OSB and Waferboard” replaced an earlier CSA standard “Waferboard and Strandboard”, and was re-affirmed in 2006 for continued reference in the codes. CSA O437.0 contains 3 grades. Grade R1 is the conventional waferboard now being phased out. Grade O-1 and O-2 are grades applicable to panels in which strands in the face layers are predominantly aligned in the panel length direction. These panels are commonly known as OSB (oriented structural board or oriented strand board). Through alignment the strength and stiffness is increased in the panel length direction. These OSB panels must be used like plywood with the panel length across supports. The CSA O437 standard includes requirements for minimum mechanical and physical grade properties. The tables listed on the reverse for roof, floor and wall sheathing conform to the latest National Building Code of Canada (2005 edition). For further information on the National Building Code and Provincial Building Codes please contact the Structural Board Association. TB104 TB104 7 0 mm 7.5 mm (7/8”) thick Grade O-2 panels on 800 mm (32”) joist spacing.16” 500 mm .5 mm 1/4” 5/16” 1/2” 5/16” O-1/R-1 6. it is recommended that several holes be drilled in pond area so that water will drain from floor.1/2” 12. • Leave a minimum 3 mm gap for subfloor.3/8” 12.0 OSB Type of Exterior Finish Maximum Stud Spacing Minimum Panel Mark W16 or 2R16 W24 or 2R24 2R32 / 2F16 W24 or 2R24 600 mm -24” 9.35 mm 7.0 OSB Minimum Panel Mark Combined subfloor/underlayment 1F16 1F20 1F24 O-1/R-1 15. • Roof sheathing shall be installed with the surface strands at right angles to the roof framing.9 mm CSA O325.5 mm W24 or 2R24 Vertical joints shall be staggered if the sheathing is applied horizontally.0 OSB/Waferboard Minimum Thickness O-2 15. Leave a minimum 3 mm gap between butting edges.20” 600 mm .1 mm . • If OSB subfloor is flooded due to ponding.24” CSA O325.5 mm .20” 600 mm .0 OSB/Waferboard Minimum Thickness O-2 • Siding attached to framing members furring members or blocking • Vertical lumber or stucco lath attached to sheathing • Wood shingles and shakes or vertical metal siding attached to sheathing • Asbestos cement shingles attached to sheathing 400 mm .7/16” 12.7/16” Edges Unsupported O-2 7.5 mm .3/8” O-1/R-1 9.7 mm . These panels are marked 1F32.3/8” 9.0 mm 12.5 mm .16” 600 mm .5 mm 12.9 mm 12.5 mm .5/16” 7.9 mm 15.5 mm .7/16” 11.5 mm (5/8”) under wood strip flooring. • Panels shall have T and G edges or have edges blocked by minimum 38 mm x 38 mm blocking securely nailed between framing members.5 mm . (b) Permitted with not less than 19 mm (3/4”) matched wood strip flooring laid at right angles to the supports.5 mm .16” 600 mm .24” CSA O437.7 mm (b) Nominal Imperial 5/8” 5/8” 3/4” 1/2” 1/2” With panel type underlayment 2F16 2F20 2F24 2R32 / 2F16 (a) 2R32 / 2F16 (b) (a) Permitted with wood panel underlayment or concrete topping except when finished flooring consists of ceramic tile applied with an adhesive. Sheathing to be continuous across two or more supports and with end joints staggered.1/2” O-1/R-1 9. • Install sheathing with a minimum 3 mm gap on all butting edges.5 mm 12. TABLE 2 – SUBFLOOR REQUIREMENTS CSA O437.3/8” 11.5 mm 12.1/2” 2R16 2R16 2R20 2R24 1R16 1R16 1R20 1R24 CSA O325.5 mm 15.1/2” 12.5 mm .5 mm 7.5 mm .5 mm 3/8” 9.12” 400 mm . • Some jurisdictions allow 22. Butt panels into light contact for combination subfloor/underlayment. TABEL 3 – WALL SHEATHING REQUIREMENTS CSA O437.1 mm .16” 500 mm . Joist or Rafter Spacing 300 mm .5/16” 9.5 mm .7 mm 7.1 mm .3/8” 9.0 Strandboard & Waferboard Minimum Thickness (1) Edges Supported (2) O-2 7.3/8” 11. 8 .9 mm 19. the requirements for floors shall apply. (2) Panel edges supported by 38 x 38 mm blocking or metal H-clips at mid span between framing members.5/16” 9.5 mm .24” 400 mm . with screened or textured side up.5 mm 18. However. SBA recommends minimum 15.24” 600 mm -24” 600 mm -24” 6. where flat tops are used as walking decks.7 mm .0 Construction Sheathing OSB Minimum Panel Mark Edges Supported Edges Unsupported (1) Panel thicknesses apply for pitched roofs.7 mm (a) 12. Panels to be continuous over two or more supports.5 mm Maximum Joist Spacing 400 mm .TABLE 1 – ROOF SHEATHING REQUIREMENTS Maximum Truss.