Shingle ridging is a bulging of asphalt roofing material that occurs along the joints of engineered wood panels used in roof applications. This rare phenomenon is caused by changing moisture content in the roof sheathing and occurs in traditional truss-framed roof assemblies as well as SIP roof assemblies.
The ridges caused by the expansion of SIP roof panels may be an aesthetic blemish, but it does not affect the performance of the roofing or the SIP roof panels.
Several assemblies that prevent shingle ridging are described in the Builder’s Guide to Structural Insulated Panels (SIPs). Specifying a cold roof, or simply over-sheathing the roof with an additional layer of OSB staggered over the panel joints, will eliminate the possibility of shingle ridging. Alternately, wood shingles, wood shakes, or a standing seam metal roof can be used in place of asphalt shingles.