What are the causes of building collapse?

According to The India Disaster Report 2013, the following are the major causes of building collapse:

1. The structure is not strong enough to support the load and hence it fails when it reaches a critical stress level. The structure may be weak due to its shape, size, or choice of its material.
2. The instability due to geometry, design, or material choice, will cause the structure to fail from fatigue or corrosion.
3. Failure may also occur due to improper selection of materials, incorrect sizing, improper heat treating, or shoddy workmanship.
4. Failure may also occur from use of defective materials. The material may have been improperly manufactured, or may have been damaged from prior use.
5. Vandalism, sabotage, and natural disasters can overstress a structure to the point of failure. Improper training of those who use and maintain the construction can also overstress it, leading to potential failures.

However, if the followings measures are followed, catastrophic instances can be avoided.

1. The structural designs prepared by the engineer appointed by a builder must be cross-checked by another structural engineer appointed by the municipal corporation. The municipal corporation may hire external structural consultants for the purpose. This will prevent faulty structural designs that may result in building failure.
2. The site execution of construction work, especially with respect to RCC work must be supervised by an external licensed supervising engineer appointed by Municipal Corporation.
3. Soil investigation report of the site must be made mandatory and must be conducted by a reputed institute or a laboratory. This will reduce the risk of building collapse by foundation failure.
4. The final copies of design and drawings must be given to the owners of the building for safe keeping which will become useful when any structural repairs are to be done in future.
5. Any structural repairs work or addition of new floors must be done only after consulting structural engineers.
6. For buildings which are old and which are showing signs of deterioration, immediate health check must be carried out and proper repairs must be implemented after consulting a structural engineer.

Shear and improper sub base preparation are the most of the reason