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.