One of the most common causes of structural failure is bad design. This means that someone made computational errors when designing the building, the data was inaccurate, the wrong materials were used or someone ignored how impulsive stresses affect buildings. Engineers are responsible for these failures because they are the ones who create the blueprints and design plans.
Buildings are designed to withstand specific conditions. When these conditions are exceeded, structural failures can occur. The main cause of structural failures is extraordinary loads due to weather and other natural phenomena. Examples of extraordinary loads include hurricane force winds, earthquakes, and ice and snowfall buildup. Buildings that are constructed in areas prone to these problems are designed to withstand these forces and built to be very solid. However, some types of extraordinary loads cannot be anticipated and structural failures do happen.
Faulty construction occurs when inappropriate material is used for construction. Normally, a building inspector will catch these issues and require the problem to be corrected. However, lax inspections sometimes allow faults to pass inspection. Faults that result in structural failures include bad welds, improper torque used on nuts and bolts, sand that is too salty for concrete, bad riveting and inferior steel.
The structure may be designed and built properly but if it sits on a bad foundation, failure will occur. One of the best known examples of a building with a bad foundation is the Leaning Tower of Pisa. Bad foundations cause a building to sink or lean as the earth is displaced underneath it. This displacement alters the stress distribution of the building so the construction and design are changed and no longer meet the necessary specifications.