Found these strange dirt-like veins running up my basement wall. They crumble when touched but seem hollow inside. Do I have a leak or something else?

sounds hollow when tapped or has a papery texture can indicate termite activity.
If you find piles of what looks like sawdust, these could be termite droppings, known as frass. Unlike water damage, termite damage often appears in irregular patterns and lacks the water stains or mold growth associated with leaks.

5. Simple At-Home Tests: Crumbling, Hollowness,continue reading …