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Forest Products Laboratory
One Gifford Pinchot Drive
Madison, WI 53726-2398
Phone: (608) 231-9200
Fax: (608) 231-9592


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Title: Assessing waterborne pressure treatment suitability for glued laminated beams

Source: Research in Progress. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 2 p.

Author(s)Kirker, Grant ; Hensley, Jared ; Brooks, Dallin ; Yeh, B.J.

Publication Year: 2019  View PDF »

Category: Research In Progress
Associated Research Project(s):   FPL-4723-3A

Abstract: Glued laminated timber (glulam) is not durable in exterior use unless pressure-treated with a wood preservative. The American Wood Protection Association (AWPA) has specifications for pressure treatment of glulam to impart decay resistance but does not have oversight of preservative effects on mechanical properties. Assembled glulam is most commonly treated with creosote or oil-borne preservatives, but AWPA does list one waterborne preservative for this use. APA–The Engineered Wood Association does not recommend treating assembled glulam with waterborne preservatives and cautions that doing so may void the warranty. Pressure treatment with water solutions in many ways is incompatible with glulam fabrication because the wood must be dry (~12% moisture content) to accept the resins. When glulam members are treated with a waterborne system, the wood swells. As the material dries, the shrinking causes internal stresses in the wood that cause cracks and splits. In low-humidity environments, the rate of drying can cause raised grain, checking, and cracking that damage the timber surface. The goal of this study is to better understand crack formation in glulam treated with waterborne systems and how to overcome this problem.

Publication Review Process: Non-Refereed (Other)

File size: 630 kb(s)

Date posted: 11/05/2019
RITS Product ID: 96590
Current FPL Scientist associated with this product
Kirker, Grant
Research Forest Products Technologist

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