Preface This is the eleventh edition of CSA O86, Engineering design in wood . It is presented in limit states design (LSD) format and supersedes the previous editions published in 2014, 2009, 2001, 1994, 1989, 1984, 1980, 1976, 1970, and 1959, including their Supplements. Editions of CSA O86 published in 1959, 1970, 1976, 1980, and 1984 were all developed using working stress design (WSD) theory. The last WSD version, CSA CAN3-O86-M84, Engineering design in wood (working stress design), existed concurrently with the first (1984) and second (1989) LSD versions, Engineering design in wood (limit states design). The WSD version was withdrawn on publication of the 1994 LSD edition. Three LSD editions were published in 1984, 1989, and 1994 with the CSA designation O86.1. Supplements to each of these editions were published in 1987, 1993, and 1998, respectively. Although the 2001 edition was also based on the LSD method, the O86 designation was reinstated. Significant changes in this edition include the following: • editorial changes and some reformatting and restructuring of all clauses for clarity of layout, especially Clauses 11 and 12; • revisions to design provisions for vibration serviceability of joisted floor systems; • revisions to add Structural Face-Glued Lumber grade-stamped NLGA SPS 5 and SPS 6 wood products, and Face-Glued/Finger-Joined Lumber \"Vertical Stud Use Only\" grade-stamped NLGA SPS 5 and SPS 6 wood products; • modification of Table 6.6 to revise specified strengths for Hem-Fir beams and stringers; • modification of Table 6.8 to include 38 mm × 64 mm (2 in × 3 in) dimension under the Tension Specified Strengths; • modification of Table 9.3 to add W24 rated oriented strand board (OSB); • revisions to clarify shear resistance of members with notches; • revisions to the KZc factor for sawn lumber; • revisions to the application of system factor, KH; • corrections to the limit of the length of the notch on the compression side; • updates to cross-laminated timber (CLT) terminology and symbols; • deletion of shear form factor for CLT; • revisions to maximum nail diameter for shearwalls, and new references for nails; • revisions to diaphragm configuration diagrams; • revisions to Nu for shearwall and diaphragm; • revisions to wood member thickness for nail and wood screw joints; • revisions to Clause 11.9 for the design of CLT shearwalls and diaphragms for platform-type construction; • revisions to requirements and added references to dowels in various clauses; • addition of Table A.22 for ASTM nails; and • editorial revisions to Annex B, on fire resistance of large cross-section wood elements for clarity. This Standard has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group. Scope 1.1 General This Standard provides criteria in accordance with the National Building Code of Canada, for the structural design and evaluation of structures or structural elements made from wood or wood products, including: a) graded lumber; b) glued-laminated timber; c) cross-laminated timber (CLT); d) unsanded plywood; e) oriented strand board (OSB); f) composite building components; g) shearwalls and diaphragms; h) timber piling; i) pole-type construction; j) prefabricated wood I-joists; k) structural composite lumber; l) permanent wood foundations; m) plank decking; n) nail-laminated decking; and o) structural connections. 1.2 Exclusions This Standard does not include design of timber bridges. 1.3 Design method This Standard employs the limit states design method. 1.4 Terminology In this Standard, \"shall\" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; \"should\" is used to express a recommendation or that which is advised but not required; \"may\" is used to express an option or that which is permissible within the limits of the Standard. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a Clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application. 1.5 Units If a value for measurement as given in this Standard is followed by an equivalent value in other units, the first stated value is to be regarded as the specification.