The reason to cause foundation failure:
Settlement - The problem may arise with extensions if the foundations of the extensions are not the same depth as those for the rest of the property. ie the downward movement of the soil due to the load of the building. The crack usually occurs within the first few years of the property being built and then will stabilize.
- Subsidence - often found in clay soil and it only occurs at a later date after any settlement has been ceased. usually, affects part of the building.
- subsidence is commonly related to underground activity, leakage of water from drains, leakage of water from burst water pipes and the growth of tree roots, especially in clay soils.
- Hogging - take place where the moisture content of clay increases under a building.