Repairing an exterior crack requires the installation of a waterproof membrane or liquid applied to the foundation wall, starting at the base of the foundation all the way up to ground level. A drain panel must also be fitted to remove any water pressure on the outside wall. This should effectively direct the accumulation of water to the contour of the perimeter towards a functional french drain.
Older buildings usually have foundation walls made of stone or rubble, even mortar joints that become brittle over time.
When there’s poor drainage, or lack of a drainage system, the freezing and thawing cycles contribute to burst the mortar due to the water accumulation in it.
Eventually the water will eventually seep inside. Result: water that soaks the mortar will freeze and burst the seams. The best way to protect this type of foundation is establishing a functional drainage system and waterproofing the foundation, provided that the condition of the outside foundation is right.
Same goes for a foundation built of concrete blocks. Waterproofing is the only solution to prevent water infiltration.