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.