It is very unusual for cracks to appear on the foundation walls. Cracks signify problems or damage affecting the walls. These problems are mainly caused by shrinkage in the foundation and soil settlement or expansion. Earthquake can also cause cracking. The shape and the size of the crack can be used to establish the cause of these problems. You should, therefore, know the cracks are ‘read’ to determine the severity of the situation. This would also help you when deciding on the action to take.
Any crack which might appear on the walls should be repaired. Concrete might shrink during the curing process. Curing is a chemical reaction and is not necessarily caused by loss of water. The amount of shrinkage on the concrete walls is dependent on some factors which include; type of the concrete used, prevailing temperatures and the amount of water used. Below are the common types of foundation cracks in buildings.
Vertical cracks
These are the thin cracks 
which occur randomly in the foundation walls. Their length ranges from a few inches. The entire wall might also get these cracks. You are more likely to find these cracks in those areas where concrete was poorly or incorrectly mixed the concrete. The lack or use of steel reinforcements also influences the characteristics and degree of cracking in buildings. Shrinkage cracking stops once the concrete curing process is complete.
Cracks in older building
Any crack which might occur in the older building should be taken very seriously. …