Common causes of the foundation failure
The foundation is the most important single component of the structure that is directly responsible for the stability of a building. There are many reasons that foundations can fail. Generally speaking, any excessive force that causes the foundation to move (vertically or laterally) can have a destructive effect and cause foundation failure. There are several common causes of foundation failure and they are as follows:
• Excessive lateral pressure (see photo)
• Soil vertical movement (settlement or heaving)
• Undermining of the foundation supports
• Change in water table elevation around the building site
• Load transfer failures
• Slope failure
• Excessive vibration near building vicinity (due to nearby construction, etc.)
• Design error
• Poor construction
• Natural disasters (earth quake, flood, etc.)
Excessive lateral pressure and differential settlement are two major mechanisms of a foundation failure.
Failure due to lateral movement caused by excessive hydrostatic pressure
One of the common causes of lateral wall movement is excessive water accumulation behind the wall. If the property does not have proper grading and drainage installed around the building, heavy frequent rain falls can cause water pressure to build up near the foundation walls. Typically, house foundations are not designed to withstand substantial hydrostatic (water) pressure. Therefore, after some period of time, the weight of the water in the soil pushing up against the foundation will cause the foundation to move inward. Wall horizontal cracks and wall bowing in conjunction with multiple diagonal cracks are typical indicators of the foundation movement due to excessive lateral pressure.
Failure due to differential settlement (see photo)
Frost is one of the common causes for the foundation to move in a vertical direction. When the ground freezes in the winter, water found in the soil turns into the ice. The ice formation is accompanied by volume increase and causes the ground to expand. If this occurs near, or under a foundation, it can cause the foundation to move in a vertical direction. Since water concentration in soil is different throughout the site, the foundation will move at the different rate along its length. This process is called a differential movement and may cause the foundation to fail. Therefore, it is critical to construct new foundations below the frost elevation.
Signs indicating that the structure may have foundation problems:
• Sloping or uneven floors, cracks in floor tiles
• Spaces between wall and ceiling or wall and floor (see photo)
• Doors and/or windows do not close or close properly (see photo)
• Horizontal, vertical and/or diagonal cracks in exterior (see photo) or interior walls (see photo)
• Wall separation and/or rotation from the rest of the structure (see photo)
• Cracks or bowing of foundation walls (see photo)
What to do if you think that your home is experiencing foundation problems:
Contact a Structural Engineer as soon as possible. Only a Licensed Professional Engineer can render an opinion as to the structural integrity of the foundation.
Most people make a mistake and turn for help to the Contractor first. It should be noted that the Contractor, who may have experience in repairing the foundations or other structural failures, has no qualifications to provide the building owner with solutions to their structural issues. Therefore, the reputable Contractor will turn for help to the Structural Engineer as he (Contractor) knows that all structural work involves obtaining a Building Permit from the local Authority. In order to issue a Building Permit, most Authorities require the structural drawings that are sealed and signed by the Licensed Engineer. Thus, first getting the Engineer involved saves the building owner time and money. Once structural repair drawings have been developed by the Engineer, the owner may start soliciting bids from multiple Contractors. This will ensure a fair bidding, as Contractors compete for the same work.
Structural problems call for professional solutions. If you think that you have a structural issue, such as a foundation problem, contact a Licensed Professional to properly address it.