Why does an inspector note shingles that have lost their tab alignment across a slope?

Asphalt shingles are installed in straight courses with consistent offsets, because that is how the manufacturer's coverage and exposure pattern works. Straight when new means that any wandering seen later is movement that occurred after installation, and there are two ways it happens. The shingles themselves can slip, when fasteners were driven high, driven through the wrong part of the shingle, or have backed out and lost their grip. Or the deck beneath can have moved — truss uplift lifting a section seasonally, sagging between rafters, or a structural change telegraphing through. The distinction matters because one is a covering repair and the other points at framing. That is why the inspector reads misalignment as a movement indicator rather than a cosmetic one, and looks from inside the attic to see which of the two it is.

Shingles are laid in straight courses when new, so wandering alignment is evidence of later movement — either shingles slipping from failed fastening or the deck beneath deforming.

Asphalt shingles are installed in aligned courses with specified exposure and fastener placement. Later misalignment indicates post-installation movement, from fastener failure or deck deformation such as truss uplift or sagging.

Straight When New. If the courses wander now, something moved — either the shingles slipped or the deck did.

Truss uplift produces seasonal movement: the pattern appears in winter and relaxes in summer. Interior ceiling cracks at partition walls corroborate it.

• •Reporting misalignment as cosmetic
• •Not going into the attic to identify the cause
• •Assuming slipped shingles when the deck is the source