Longitudinal Shrinkage of Western Redcedar, Western Hemlock, and True Fir

Longitudinal shrinkage of western redcedar, western hemlock, and true firs is within the range of values usually given for this property. Average longitudinal shrinkage from green to OD condition was 0.15 percent of the green dimension for the redcedar, and 0.11 percent for the western hemlock and true firs. With all three woods, most of the shrinkage occurred below about 12 percent MC. Longitudinal shrinkage is highly variable. Many pieces of these woods swell somewhat in drying to about 12 percent MC. Except for an occasional piece, shrinkage of western redcedar lumber dried to a maximum of 19 percent MC should not exceed 0.04 percent on further drying to exterior conditions of about 12 percent MC. Under the same conditions, shrinkage of western hemlock and true firs should not exceed about one-half as much as redcedar. Assuming about 6 percent EMC for interior uses, western redcedar lumber dried to 12 percent maximum MC should shrink no more than 0.09 percent in use, except for an occasional piece. Under these same conditions, western hemlock and true firs should shrink no more than 0.06 percent and 0.05 percent.

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