Common problems of existing foundations

Existing foundations commonly suffer from the following problems.

1. Settlement: Uniform or differential settlement from consolidation of soil, weak strata, heavy loads or extra floors added; it causes cracks in walls and floors, tilting, and door and window jamming.
2. Cracks in the foundation, plinth and walls from settlement, soil movement or earthquake.
3. Dampness: Capillary rise because DPC has failed or was never provided; water table rise, leaking drains.
4. Deterioration of materials: Sulphate attack on concrete, corrosion of reinforcement, rotting of timber, and weathering of stone and brick.
5. Soil movement: Swelling and shrinking of expansive soil, erosion of soil from the base, scour near rivers and drains.
6. Overloading due to change of use or vertical extension without checking capacity.
7. Effect of nearby work: Excavation, construction of neighbouring building, pile driving, vibration, blasting.
8. Tree roots and water table lowering causing shrinkage settlement.
9. Landslide or slope failure on hill sites.
10. Earthquake damage and liquefaction.

Remedies

Underpinning (pit method, pile method), enlarging the footing, grouting, soil stabilisation, drainage improvement, repair of cracks and DPC, chemical injection, and strengthening by jacketing.