Residual Extractives in Western Red Cedar Shakes and Shingles after Long-Term Field Testing

Western red cedar shakes and shingles were analyzed for extractives after 25 and 33 years of exposure in a field test to better understand the extractives associated with long-term durability. Only minimal concentrations of thujaplicins were found, but plicatic acid was still present in significant quantities. Plicatic acid or other uncharacterized compounds that remain in the wood may play a more important role in the durability of shakes and shingles than previously thought.