Don’t fret; it is normal for foundation plaster to crack. That being said, foundation plaster does not crack on its own, but only when acted upon by other forces.
Plaster is a 1/16 inch coating of cement used to help cover the unsightly seams and unevenness caused by foundation forms. It is troweled onto the face of an exposed area of your foundation wall. If you see a crack in your foundation plaster, it is likely an expression of something else going on, but it’s not always bad.
Stress cracks in a foundation wall will show through the plaster. When a foundation wall has cracked through due to stress or movement in the foundation wall, the plaster will also crack. Cracks in a foundation wall are not dissimilar to cracks in stucco, driveways, and most other cement products. It is unfortunate but normal. Where a foundation wall has not moved, the plaster is almost always in great condition.
In some cases, the foundation cracks have caused the plaster around the crack to pop, bubble, or flake off, as shown in the pictures below.
These areas can be recovered to repair the popped off plaster. However, if the crack in the foundation is due to movement in the foundation wall, even if ever so slight, the crack in the foundation will show in the plaster again and there is nothing to stop this. As such, cracks in plaster due to movement in a foundation wall are not covered by a warranty.