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Effect of moisture content on warp in hardwood 2 by 6`s for structural use


William T. Simpson
John W. Forsman



Publication type:

Research Paper (RP)

Primary Station(s):

Forest Products Laboratory


(Research paper FPL ; RP-580):8 p. : ill. ; 28 cm.


Sugar maple (Acer saccharum), red maple (Acer rubrum), and yellow birch (Betula alleghaniensis) 2 by 6as were dried and evaluated for warp as it affects ability to meet softwood dimension lumber grading rule requirements for warp. In the first part of the study, sugar maple was kiln-dried to three levels of final moisture content: 27%, 19%, and 12%. Warp during kiln drying increased as final moisture content decreased. Following kiln drying, the lumber was planed and then equilibrated in 12% equilibrium moisture content conditions. Warp during equilibration generally increased as the final moisture content after kiln drying increased. Crook, bow, and twist did not increase enough during equilibration to cause much structural lumber grade loss from warp. However, the percentage of boards still meeting structural lumber grade limits for cup fell to about 80%. In the second part of the study, sugar maple, red maple, and yellow birch 2 by 6as were air- and predried to 27% moisture content and, in general, did not suffer much grade loss during equilibration.


Simpson, William T.; Forsman, John W. Effect of moisture content on warp in hardwood 2 by 6`s for structural use. (Research paper FPL ; RP-580):8 p. : ill. ; 28 cm.

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