Hairline cracks are thin, shallow, and often cosmetic; structural cracks are wider, migrate through layers
https://knoxodpo629.cavandoragh.org/how-high-grade-window-caulking-prevents-severe-moisture-rots
Hairline cracks are thin, shallow, and often cosmetic; structural cracks are wider, migrate through layers, or shift over time. Measure width, monitor growth, and inspect nearby framing to determine repair urgency.