Losses Incurred in Drying and Dressing Lumber in the Southern Interior of British Columbia

Losses during drying and dressing of lumber produced by southern interior mills of British Columbia were calculated using the following method. Lumber was selected at random from the green chain and parcels were marked for later observation. After 70 days of air-drying in the summer and dressing, the lumber was graded and tallied. Any piece that had changed grade was noted and the rough green grade was determined. Green and dry measurements were taken. The same was done for lumber which was kiln-dried. The loss in board foot volume for the air-dried samples was 2.5 percent. The losses in board foot volume were classified according to their cause. Causes were natural trim, seasoning trim, manufacturing trim, and manufacturing thinness. Natural trim takes place after drying to improve the grade of the piece. Seasoning trim removes defects related to the drying of the lumber. Manufacturing trim eliminates defects caused in manufacturing. Thinness reflects loss in volume due to seasoned boards that are too thin to qualify for the grade without remanufacture. Seasoning degrade which took place during air-drying accounted for nearly half of the total loss in value of limber that had been air-dried. Total loss for air-dried lumber of all species was $6.40. Seasoning degrade in kiln-drying accounted for less than 20 percent of the total loss in value but kiln-dried lumber required twice as much seasoning trim as air-dried lumber (primarily to remove end checks), which somewhat offset the advantages of kiln-drying. However, the total loss in value for kiln-dried lumber was $3.60. Spruce (Picea spp.) and white pine (Pinus monticola) had higher dollar losses for both air-dried and kiln-dried lumber than Douglas-fir (Pseudotsuga menziesii) or Ponderosa pine (Pinus ponderosa). There were other losses from cutting lumber larger than needed. Forty percent of the Douglas-fir dimension stock had been cut oversize.

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