Prior to the 1970s, the design values of Canadian dimension lumber were determined by testing small clear samples.
Beginning in the 1970s, new data was gathered on full-size graded lumber, known as in-grade testing. The in-grade testing program involved testing thousands of pieces of dimension lumber grades to destruction in order to determine their in-service characteristics. Resulting in the establishment of new relationships between species, sizes, and grades.
In the early 1980s, the Canadian lumber industry combined the in-grade testing with a major research program for bending, tension, and compression parallel to grain strength properties of 2-inch thick nominal (38 mm) dimension lumber for Select Structural, No.1, No.2, No.3 of the commercially important Canadian species groups; Spruce-Pine-Fir (S-P-F), Douglas Fir-Larch (D.Fir-L) and Hem-Fir. This provided the basis for extending the results to the full range of dimension lumber grades and member sizes described in CSA-O86 Engineering Design in Wood.