Exterior cracks in home concrete walls may be easily repairable or dangerous, depending whether or not the crack is spreading. Hairline cracks can be repaired, but if the crack is spreading, then professional help is needed.
If you suspect a crack larger than a hairline is spreading, then professional help is called for. Put a piece of tape over the crack, and if it tears, the crack is spreading.
Hairline cracks are not serious if they are not spreading. These can be repaired with an injection of urethane or epoxy.
Spreading cracks can be very serious, leading to more and more damage the longer they are ignored.
Wide cracks that are not spreading can be repaired with sand and epoxy sand filler. If the crack is extremely wide, be sure to contact a professional.
Concrete Block Walls
If your walls are block walls but not poured concrete, then use an epoxy sand filler for repairs.