Design Values

The National Lumber Grades Authority (NLGA) establishes and monitors structural lumber design values of Canadian species.  These lumber design values are approved by the CSA-O86 Technical Committee on Engineering Design in Wood for use in Canada and by the ALSC Board of Review for use in the U.S.     To facilitate marketing in the U.S. the NLGA Grade Rule incorporates the National Grading Rule for Dimension Lumber (NGR) which establishes standard lumber grades and grade names for all commercial species of dimension lumber produced in Canada and the U.S.  CSA-O86 provides the criteria for the structural design and appraisal of structures or structural elements made from lumber graded in accordance with the NLGA Standard Grading Rules for Canadian Lumber and identified by a CLSAB Accredited Agency grade stamp as outlined in CSA-O141.  CSA-O86 employs the “Limit States Design” method which evaluates for safety at the ultimate load and serviceability at the working load.

These specified strengths and modulus of elasticity are based on extensive testing performed by the lumber industries in Canada and in the United States. Their joint comprehensive program involved testing thousands of pieces of dimension lumber to destruction to determine their in-service characteristics.

The values given above apply to lumber that is graded in accordance with NLGA Standard Grading Rules for Canadian Lumber. Lumber should be identified by a grade stamp applied under the supervision of a grading agency accredited by the Canadian Lumber Standards Accreditation Board, in accordance with the provisions of the CSA Standard CAN/CSA-O141.

The values shown are intended to be used by qualified designers, in conjunction with the appropriate adjustment factors found in the CSA-O86 Standard. Design tables, examples and background information can be found in the Canadian Wood Council’s Wood Design Manual which includes a copy of CSA-O86 supplemented with commentary material.

Please refer to the CWC website for more information: www.cwc.ca