Cupping & Curling
Will premium grade give the least chance of curling over time?
As the grain that runs down the shake is perpendicular to the surface at the butt, premium grade will not curl as easily as material that allows some flat grain.
Why are some of my shakes starting to cup, curl, bow, or warp?
Some curling on a shake roof is normal since cedar shakes are a natural material. Excessive cupping and curling is usually due to improperly placed nails, too high or too far from the edge. If a competent roofing inspector/contractor determines that the excessive cupping and/or curling will affect the integrity of the roofing system, then repairs should be performed to your cedar roof. (See Repair section for further details on repairs and roof inspections).