Causes of Foundation Failure in Buildings
Foundation failure can be attributed to several things. Most commonly foundation failure is caused by the movement of expansive and highly plastic soils beneath different sections of the foundation footings. This movement can be in the form of shrinkage, which causes settlement, or expansion, which causes heave. When dry conditions prevail, soils consistently lose moisture and shrink. When moisture levels are high, soils swell. Regardless of the nature of the movement, it will most likely manifest itself in the form of visible cracks in the foundation walls, exterior brick walls, or interior sheetrock or plaster walls. Officially, any structure movement is known as differential settlement.
In addition to expansive soils, subsurface peat, which has a low bearing capacity and deteriorates over time, can also cause differential settlement. Other soil types such as sand and silt also have lower than required bearing capacities.
Poor drainage from yard run-off and gutter downspouts discharging at the base of the foundation are among other causes. Excess moisture around the foundation can cause the soils to become over-saturated and lose “bearing pressure,” or the strength to support weight. When this happens, structures “settle” or sink into the ground.
If soil and water control problems weren’t bad enough, there is also the issue of transpiration. Transpiration is a fancy word for the process of trees and large plantings absorbing the water from the soils beneath and around your home. During an active season, roots extending beneath and around the footings of the house can remove moisture from the soil, causing it to become desiccated. Again, where expansive soils exist this removal of moisture will cause soil shrinkage and settlement.
Plumbing leaks are another major contributor to foundation settlement. Inundating the foundation with water from your home’s pipes will cause foundation failure, as would poor drainage on the outside.
Poor construction sometimes causes settlement in homes, but only rarely.