What are foundation problems with timber piles?

Foundation problems with timber piles are forms of decay and overloading that reduce the load-bearing capacity of the foundation. The main ones are pile rot, bacterial decay and negative skin friction.

The main problems

Pile rot is caused by fungal decay when pile heads dry out due to a groundwater level that drops too low (dry standing). Fungi need oxygen and therefore only attack dry or damp wood above the water line; as long as piles remain permanently submerged, they are in principle protected. A second problem is bacterial decay. Bacteria can attack even permanently wet pinewood piles, softening the wood from the inside so that the pile gradually loses its strength. In addition there is negative skin friction: settling soil around the pile hangs onto it and creates extra load, which can lead to overloading.

Application

The consequences of these problems are noticeable in the home: settlement, cracks in walls and sticking doors and windows. When investigation shows that the decay has progressed too far, foundation repair is required to prevent the risk of collapse. Detecting issues early through a foundation survey limits both damage and cost.

Related terms

• Pile rot
• Pile bacterial decay
• Dry standing
• Groundwater level

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