The premature removal of treated wood from service, due to weathering (checking, distortion and UV degradation), rather than decay has led to increased acceptance of products promoted as low maintenance. Wood-plastic composite decking in the USA is anticipated to post 15% annual growth through 2009 to almost 900 million board feet (Freedonia Group 2003). Plastic and wood-plastic composite lumber are projected to capture 25% of the decking surface board market in the USA. This is a direct threat to the approximately 2 million cubic metres of softwood lumber annually treated with copper amine-based wood preservatives for residential and commercial exterior products. These products have also raised the bar for performance and price, 2 to 3 times that of wood decking. There is a considerable amount of research underway to develop methods to improve the serviceability of decking. These include: material sorting, profiling, water repellants and coatings. Current standard test methods focus entirely on durability and do not take appearance into account. Standard test methods are therefore needed to evaluated processes designed to improve serviceability.
Canadian wood preservations standards do not include any test methods and instead reference the American Wood Protection Association (AWPA) standards. The AWPA has recognized a need to update their standards in the area of serviceability and has set up task forces on test methods and performance criteria. These task forces will be the venue for review, revision and further development of these standard tests. FPInnovations has been conducting tests of deck boards for many years and has included evaluation of checking in some of these tests. FPInnovations has also been conducting tests of coatings and the underlying substrate using methods adapted from those of the USDA Forest Products Laboratory. Elements of these methods have been put together and further developed to create a standard serviceability test using a decking module.
One of the most important characteristics of wood is its tendency to check due to weathering. However, it can take several months or years under natural conditions for significant checking to occur. Hence an accelerated predictive testing method is urgently needed. Dr Phil Evans, formerly of the Australian National University, now with the UBC Centre for Advanced Wood Processing is one of the few researchers that has focussed on the issue of checking. He has developed a prototype accelerated checking machine that shows promise as a screening tool for processes to improve serviceability.
Report #1 presents results on serviceability of a service trial of profiling and coating after one year exposure using the inspection methods in a draft AWPA standard test for serviceability. The draft standard is attached as an appendix to this report.
Report #2 describes the work done to develop an accelerated test method.
Report #3 presents results on an accelerated test of profiling using the inspection methods in a draft AWPA standard accelerated test method. The draft standard for this accelerated test is attached as an appendix to this report.