Hairline cracks are thin, shallow, and often cosmetic; structural cracks are wider, migrate through layers

https://andreeiec711.theglensecret.com/how-to-protect-your-home-foundation-with-proper-parging

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.