Some small wall cracks leak during heavy storms; others do not. The appearance and movement of the wall matter as much as the moisture.
Document the crack
Photograph the crack and note whether it changes or becomes wet after rain.
Avoid a one-size repair
Surface patching alone may not address an active leak or wall movement.
Know the limit of waterproofing
Wide, displaced, bowing, or rapidly changing cracks warrant qualified structural assessment.
What to do before hiring
Photograph the affected area and record when moisture first appears. Ask the person assessing the basement to distinguish water entry from condensation or plumbing, explain what the recommended work will accomplish, and identify the discharge route for any collected water.
If you see significant wall movement, widespread damage, or suspect an electrical hazard, arrange an appropriately qualified assessment before proceeding with routine waterproofing.