Adhesives for Load-Bearing Timber Structures – Classification and Performance

Adhesives for load-bearing timber structures should be chosen considering the environmental conditions in service, thetimber species, the preservative used (if any) and the production methods. The environmental impact of the adhesivemay also be a consideration. Finally, compliance with relevant standards, especially where conformance to standardsis stated or implied, is essential to mitigate risk for all interested parties.Resins based on formaldehyde chemistry are the only adhesives that meet the current standard AS/NZS 4364:1996(“Adhesives, phenolic and amino plastic, for load-bearing timber structures – Classification and performancerequirements”) [1]. Resorcinol formaldehyde, phenol-resorcinol formaldehyde and tannin formaldehyde adhesives arealso the only adhesives that are compliant with Service Class 3 (exterior conditions where the ambient moisturecontent can be greater than 18%) conditions as specified in the New Zealand and Australian standards forFingerjointed Structural Timber and Glued Laminated Structural Timber [2, 3, 4, 5]. Indeed, standards for structuraltimbers around the world have been developed based on the performance of formaldehyde-containing adhesives.