Alternative Path for Accepting PUR Adhesive in CLT JAS Standard
The Ministry of Agriculture, Forestry and Fisheries (MAFF) established a new JAS standard for cross laminated timber in December 2013 and enacted it in January, 2014. It took 20 months to draft the new JAS 3079 standard. Due to the relatively quick process of the work, the standard specifies only the adhesives that are identical to those in the existing glulam JAS standard. As a result, the CLT standard does not stipulate One-Component Polyurethane Resin Adhesive (PUR), which is the primary adhesive used for manufacturing CLT in Europe and North America. COFI has been requesting the inclusion of PUR in the standard, pointing out the potential risk of delamination of the boards when adhesives other than PUR are used As a response to this request, MAFF established a CLT JAS adhesive equivalency committee in September 2013 and held 4 committee meetings. The final meeting was held February 5, 2014 to conclude that the PUR should be accepted when adhesive or CLT manufacturers provide the technical data and committee evaluates the data as appropriate. The committee also decided that the service condition for PUR should be limited to C “A use environment where a CLT will occasionally exceed 19% moisture content; occasionally reach a high temperature by long-term exposure to solar heat or other similar conditions; and otherwise be required to have a standard level of performance in use environments where load-bearing members for structures must meet the demands for water resistance, weather resistance, and heat resistance.” The final output of the committee was the evaluation standard for the adhesives of JAS-graded CLT.