Experimental roof panels constructed using western redcedar shakes and shingles, untreated and treated with three waterborne preservatives, have been in test for 25 years at two locations in the lower mainland of British Columbia. Moderate physical deterioration in the form of erosion and splitting was present in both treated and untreated samples, but virtually all treated samples were free from decay. Minor amounts of decay were detected on some of the untreated shakes, and to a greater extent, the untreated shingles. Because the chemical loading of these treated samples is so much higher than what is currently recommended, the lack of decay is not surprising. A small study of the extractives content of untreated samples revealed that, after 25 years of service, the shakes retained more extractives than shingles, although both were at very low concentrations.