Suntree Re-Roof, 38 squares of shingles replaced, new plywood installed over exposed 1x12

Proper spacing is essential when installing plywood, 1/8" is recommended. reduces chances of "picture framing", warping, or buckling caused by movement (thermal or moisture can cause this)

This upper photo is actually the "after", below is the "before"



It is easy to see why 1x12 lumber does Not make a good base for shingles (or much else)