Cosmetic cracks vs. structural warning signs
Small, thin cracks are often cosmetic, but wide cracks, cracks that keep growing, diagonal cracks near doors and windows, or cracks paired with sticking doors or sloping floors can signal a serious structural or foundation problem.
Hairline cracks from normal settling are common and usually harmless. The ones to watch are cracks wider than about a quarter inch, cracks that grow over time, stair-step cracks in brick or block, or cracks that appear along with other warning signs like uneven floors.
Those can mean the structure is moving or under stress. If you are unsure, report the cracks to your landlord with dated photos so there is a record and the landlord can have them evaluated. Tracking whether a crack grows over weeks or months tells you a lot. If serious cracks are being ignored, a free review can help you understand your options.
This is general information about California tenant rights, not legal advice. Every situation is different.