A.Corresponding editor Paul Fisette responds: The heartwood (but not the sapwood) of both red and white cedar is naturally decay resistant. Although the two species are listed in most handbooks as having heartwood with comparable rot resistance, the experience of many carpenters suggests that red cedar is a little more rot resistant.

Several factors may account for this. When grading white cedar, it is quite difficult to distinguish between heartwood and sapwood, so it is likely that at least some sapwood slips into the all-heart grades.

Another possible factor affecting shingle durability is grain orientation. The best grade of red cedar shingles (#1) is all heartwood, clear, and vertical grained. The best grade of white cedar shingles (extra clear) is all heartwood, clear, and typically flat sawn — although, like all flat-sawn lumber, some of the material is vertical grained. Since wood shrinks and swells twice as much tangent to the growth rings as it does perpendicular to them, vertical-grain shingles lie flatter on a roof or wall after experiencing repeated wetting and drying cycles. That’s why flat-grained white cedar shingles are more prone to cupping, splitting, and failure and why I don’t recommend using white cedar shingles on a roof.

I expect 30 years of service from a high-quality red cedar roof and much less from a white cedar roof. As siding, either red or white cedar shingles, if properly installed and maintained, should last a human lifetime.