A visual condition where the roofing membrane forms raised, rectangular outlines that mirror the joints of the underlying insulation boards or roof deck panels. It is typically caused by building movement, thermal contraction of the membrane, or moisture vapor escaping through the board joints and pushing up against the membrane. While often just an aesthetic issue, severe ridging can stress the membrane and cause premature failure.
Heard on the job
You can see the picture framing across the whole roof, tracing every single piece of polyiso.