A new National Lumber Grades Authority (NLGA) standard for evaluating structural wood adhesives has been approved by the NLGA Board and will be available shortly for use by Canadian fingerjoined lumber manufacturers. Development of this document was in response to an urgent industry need to provide a procedure for evaluating structural wood adhesives other than phenol resorcinol formaldehyde or resorcinol formaldehyde (PRF/RF). While these adhesive have performed satisfactorily for many years, not having a means for evaluating newer adhesive technology severely limited the ability of Canadian glued wood product manufacturers to maintain the competitiveness of their products.
When adhesives offering lower overall manufacturing costs or light-coloured bond lines were made available to manufacturers of competing wood products, Canadian manufacturers were not able to take advantage of these adhesives. This forced Canadian manufacturers to use overseas or US adhesive standards. While this provided a solution, it created an awkward situation where Canadian production could not be used in Canada because the adhesive did not meet the requirements of the Canadian wood product standard and thus the Canadian building code.
The development of the new NLGA adhesive standard occurred in two stages. The first stage, which was funded under the Canadian Forest Service Value-Added program, consisted of the following: a survey of industry stakeholder needs; a review of existing North American and overseas structural wood adhesive and glued wood product standards; and drafting and verification of the proposed standard in an inter-laboratory test. Two working groups were established: an Industry Working Group (IWG) consisting of several Canadian lumber and glued lumber producers; and an adhesive manufacturers group consisting of several Canadian and US manufacturers of wood adhesives. At the completion of the planned program, it was the opinion of the project team that the proposed standard and supporting technical information could only be used to assess structural wood adhesives for dry service conditions. Although it was estimated that nearly all of the glued wood applications, especially those involving alternative adhesives, would be for dry service conditions, the IWG and the NLGA Standards Committee (NLGASC) recommended that additional effort be put into developing a standard that would be suitable for wet or exterior use.
The rationale for this request was that although most of the applications would be for dry service conditions, the need to mark the product as being only suitable for such conditions would give the end-user the appearance that the product is “inferior” to a competing product without such markings. This would be the case in the US market where a US producer using the same adhesive would not be required to mark the product as “intended for dry service conditions only”.
The research program was subsequently extended, which is the subject of this report.