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E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page. Contact us to discuss advertising or to report problems with this site. Copyright © 1996-2014 - WOODWEB ® Inc. The editors, writers, and staff at WOODWEB try to promote safe practices. WOODWEB, Inc. 335 Bedell Road Montrose, PA 18801 Contact WOODWEB. Outdoor to Indoor Temperature Rise and Relative Humidity. Wood Shrinkage Calculator at WOODWEB. Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement Letters, questions or comments?
E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page. Contact us to discuss advertising or to report problems with this site. Copyright © 1996-2014 - WOODWEB ® Inc. The editors, writers, and staff at WOODWEB try to promote safe practices. WOODWEB, Inc. 335 Bedell Road Montrose, PA 18801. Understanding Moisture Content and Wood Movement. (with Gene Wengert, The Wood Doctor.)
Expected movement can be accurately predicted, which means avoiding potential problems down the road. In this article, we’ll explain the importance of understanding wood movement, how to use a moisture meter to measure the moisture content (MC) of trim, how to decide when a load of trim should be rejected, and how to accurately estimate how much trim will move after it’s installed. Most finish carpenters are aware that seasonal changes in humidity cause trim and flooring to shrink in the winter and expand in the summer. But few realize that the expected movement can be accurately predicted and potential problems avoided.
It’s our premise that with a moisture meter and an understanding of wood movement, most wood movement problems can be avoided. Wood Movement — You Can’t Stop It Wood is hygroscopic, which means its MC will fluctuate based on the relative humidity (RH) of the surrounding air. Wood Movement. MOISTURE CONTENT AND MOVEMENT Wood moves as its moisture content changes.
In a tree that’s just been felled, the wood is “green” — sap fills the cell cavities. This free water (as the sap is sometimes called) accounts for 72 percent of the total moisture content, although this percentage may vary from species to species. The remaining 28 percent saturates the wood fibers in the cell walls. This bound water in the fibers causes them to swell, just as a sponge swells when you wet it. As the green wood dries, the free water evaporates first, then the bound water. Wood dries to an average moisture content of between 4 and 11 percent, depending on the area of the country, but it never really comes to rest!
In green wood, free water fills the cell cavities and bound water saturates the fibers in the cell walls. The moisture content of the wood varies with the relative humidity of the surrounding air, as this chart shows. GME_Wood_Land/GME_Woodworking_Stuff/0_Techniques_Information/Joinery/13_Wood_Movement.pdf. Understanding Wood REV/E - R Bruce Hoadley. WS/Articles/Wood-Movement-Charts.pdf. Www.woodweb.com/knowledge_base/fpl_pdfs/fplrn268.pdf.