Compression Strength Adjustments for Moisture Content in Douglas-Fir Structural Lumber


  • J. D. Barrett
  • Wilson Lau


Moisture content, compression strength, structural lumber


The effect of moisture content on the compression parallel to grain strength of Douglas-fir dimension lumber was evaluated using full-size on-grade members. Compression parallel to grain strength properties increased with drying throughout the entire property range.

The influence of moisture content on compression strength was observed to be strength level dependent. Linear and quadratic surface models are used to represent the relations between member moisture content and compression strength (or capacity) as a function of property level. Model parameters were derived using a Douglas-fir data set. Douglas-fir results are compared with the limited data available for the hem-fir and S-P-F commercial species groups. The comparisons suggest that the relationship between compression strength and moisture content is generally consistent for these species.


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Research Contributions