Design Values

The National Lumber Grades Authority (NLGA) conducts resource monitoring as described in ASTM D-1990 to establish design values as required by CSA-O-86 and the National Building Code of Canada.  CSA-O-86 (Engineering Design in Wood) outlines the criteria for structural design and appraisal of structures and/or structural elements made from wood.  CSA-O-86 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-0141.

The values shown are intended to be used by qualified designers, in conjunction with the appropriate adjustment factors found in the CSA 086 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 086 supplemented with commentary material.

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