As a continuation of a project to develop a large scale accelerated laboratory test for the durability evaluation of materials used in the construction of preserved wood foundations, hemfir plywood panels treated to two retention levels with CCA-C and ACA preservatives and installed in PWF test boxes at the Ottawa laboratory are being examined for durability performance after four years in service. This interim progress report has been prepared pending completion of the inspection, at which time a final report will be prepared.
According to the CSA 080.15 Wood Preservation Standard dealing with treatment of material for preserved wood foundations (PWF), treated wood that is cut or machined in the field must be protected with an application of a commercial field cut preservative, usually 2% copper naphthenate solution. In order to determine if present practice in using copper maphthenate is an effective means of protecting cut edges of PWF grade plywood, a number of CCA-C and ACA treated hem fir plywood stakes were prepared and coated with a 2% copper naphthenate solution on their cut edges according to the standard. These stakes were then installed in the Ottawa test plot for durability performance evaluation. An equal number of stakes were also installed into the PWF test boxes currently undergoing evaluation at the Ottawa laboratory in order to expose the stakes to an accelerated decay environment and to establish a correlation between the decay hazard in the test boxes and that in a normal test plot. An initial inspection of the test stakes has indicated that untreated control stakes in some test boxes had failed after only four months of service, indicating a significant increase in the decay hazard in the test box environment. Stakes will continue to be rated for performance on a period of years. The durability performance data generated will provide the information necessary to determine if commercial 2% copper naphthenate solution is providing an adequate level of protection to treated PWF grade plywood. Results will be reported to appropriate CSA committees.