I didn’t inspection this home. It was across the street from one I was inspecting. 1st pic is over garage area and 2nd pic is over living space.

Has anyone ever seen this and knows what causes it: too thin of sheathing used over rafters?

Butt joints to close to allow for expansion.

Moisture is the major cause of edge buckling of the roof deck. I bet there is no moisture barrier under those shingles and the attic ventilation is poor. That roof is FUBAR.

Plywood and OSB come from the mill in strapped bundles (sometimes) wrapped in plastic at about 4-6% moisture content. Even when it’s not wrapped in plastic, the top and bottom sheets act as a barriers to moisture absorption except through panel edges. If it rolls off the truck and gets installed on the roof immediately and the shingles are installed right away they will buckle as the roof sheathing expends as it adjusts to the jobsite humidity, which is pretty much always higher than 4-6%. Sheathing needs time to adjust to local conditions before shingles are installed.
Properly stated, “Roof sheathing should have time to reach equilibrium moisture content (EMC) with the jobsite environment before shingles are installed.” This is why they recommend leaving 1/8" between panel edges during installation.

That is really ugly.

O’boy, nothing like knowing exactly where the sheets butt up. Makes putting roof vents in a lot easier, no need for a tape.

Totally agree with everything said. That’s a costly mistake.

Would use of H clips have helped ?

those aren’t use at the top chords only at span

Yes, that would have helped the horizontal lines. I’ve been building a long time and that’s the worst I have seen. I wonder how many homes this guy did as I would assume you could drive around and see his trademark sheathing work.

Maybe. Panels are in direct contact with each other at every H-clip, so in effect, they butt tight to each other every 24". H-clips are designed to support panel edges in rafter bays rather than create expansion gaps.

I drove by the same home again today and “STILL CAN"T FRIGGEN BELIEVE IT”.