In the 3-year rotation of subject matter for the reports of the "Durability of Wood" project, attention has again turned to treated commodities. In these tests, we evaluate not only the efficacy of the wood preservative, but also the effect on performance of the quality of treatment that can be achieved with Canadian wood species. The collection of long-term performance data takes time and it is impossible to predict questions about standards for which answers will be needed in 10 or 20 years' time. Consequently, Forintek has maintained a comprehensive field-testing program covering a wide range of commodities, wood species, preservatives and treatment methods. The reports in this compilation cover decking, finger-jointed lumber above ground, shakes, millwork, fence posts, lumber in a termite area and needle-incised lumber in an accelerated ground contact test.
Softwoods - Preservatives
Glued joints - Finger - Preservation
Preservatives - Chromated copper arsenate (CCA)
Preservatives - Penetration
Preservation - Durability
Decking - Preservation
Shingles - Preservation
Thuja plicata - Shingles
Shingles - Durability
Preservatives - Ammoniacal copper arsenate (ACA)
Posts - Preservation
Preservation - Incising - Tests
Picea - Preservation
Pinus contorta Dougl. var. latifolia - Preservation
A series of long-term field tests have been evaluating the performance of various preservative treatments for shakes and shingles. This report updates the performance data for these products. CCA continues to be highly effective in protecting shakes. After 45 years in test, western redcedar shakes treated with CCA-B remain serviceable. After 20 years in test, pine and spruce shakes, treated with CCA, had no confirmed decay. ACQ-D and CA-B were effective in protecting western redcedar shingles, with little decay observed after 15 years of exposure. Propiconazole and oxine copper were associated with greater levels of decay and would not be recommended for protecting western redcedar shingles at the retentions evaluated. Longer exposure time is needed to evaluate the efficacy of the DDACarbonate and alkylamine oxide treatment.
A field test under natural weathering conditions of pine, spruce, and aspen shakes, both untreated and treated with CCA-C, was established in 1995 at Vancouver, BC. Untreated western red cedar shakes were included as reference material. The shakes were inspected for decay and dimensional stability after five years of exposure. The CCA-treated samples were free of fungal attack and decay of the untreated wood was limited. In terms of splitting, untreated western red cedar was superior to the other species. Pine, both untreated and CCA-treated, was less split than spruce and aspen. CCA-treated spruce was more split than untreated, but splitting was not affected by CCA treatment in pine and aspen. In terms of erosion, untreated pine and spruce were equivalent to western red cedar while aspen was more eroded. CCA treatment reduced erosion of the shakes surface in the three species compared to untreated samples. In terms of cupping, untreated pine was equal to cedar while spruce and aspen were more cupped than pine and cedar. CCA treatment did not affect the degree of cupping.
After five years of exposure in a field test in southwestern BC, second growth western red cedar shingles treated with waterborne preservatives alternative to CCA-C are in excellent condition, with no visible decay. Untreated shingles are also still in very good condition.
FPInnovations has a number of long-term field tests of wood roofing material set up at different times. Experimental roof panels of western redcedar shakes, untreated and treated with chromated copper arsenate type B (CCA-B), have been in test for 40 years in the lower mainland of B.C. No decay, and only moderate erosion and splitting, are present in treated samples, while untreated shakes would have required replacement after twenty years.
Pine, spruce, and western redcedar shakes were inspected for decay and dimensional stablility after 15 years of exposure at Vancouver, B.C. The CCA-treated samples were mostly free of fungal attack, while decay of the untreated pine and spruce was advanced. In terms of splitting, untreated western redcedar was superior to other species. Splitting was not affected by CCA treatment. In terms of erosion, there was little difference between the untreated species and CCA treatment reduced erosion of the shake surface.
After ten years of exposure in a field test in southwestern BC, second growth western redcedar shingles treated with waterborne preservatives considered as alternatives to CCA are in excellent condition, with virtually no visible decay. However, ACQ and CA-treated shingles do show substantially darker colour than typical for CCA-treated and untreated shingles. Untreated shingles are also still in very good condition.