- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 17 Apr 2018
Foundations provide support for structures, transferring their load to layers of soil or rock that have sufficient bearing capacity and suitable settlement characteristics to support them. Very broadly, foundations can be categorised as shallow foundations or deep foundations.
Pile foundations are a type of deep foundation, formed by long, slender, columnar elements typically made from steel or reinforced concrete, or sometimes timber. A foundation is described as 'piled' when its depth is more than three times its breadth.
Pile foundations are principally used to transfer the loads from superstructures, through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth. They are typically used for large structures, and in situations where soil may be subject to excessive settlement.
Friction (or floating) piles develop most of the pile-bearing capacity by shear stresses along the sides of the pile, and are suitable where harder layers are too deep to reach economically. The pile transmits the load to surrounding soil by adhesion or friction between the surface of the pile and soil, which in effect lowers the bulb of pressure. In other words, the whole surface of the pile (cylindrical in shape) works to transfer the forces to the soil.
To gain a better understanding, consider a nail that is driven into a piece of timber. The nail becomes more secure and tightly fastened into the timber, the further in that it is driven. The greater the embedment depth in the ground, the more load the pile can support – the load-bearing capacity of the pile is directly proportionate to its length.
For more information see: End-bearing piles.
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
What to bear in mind when claiming damages in construction.
How do we achieve sustainable clean-water infrastructure for all?
What you should know when appointing an architect.
A brief history plus some new developments.
How computational fluid dynamics (CFD) helps building design.
The Hong Kong Harbour Area Treatment Scheme (HATS).
'Expressions of interest' for construction contracts.
Dame Judith Hackitt confirmed as keynote speaker – one year on from the Hackitt Report. Save £100 on tickets.
House of Lords committee calls for investment in housing, transport, education and infrastructure.
Supporting assets that are crucial to achieving business goals. Free download.
We've created a custom search engine for the construction industry. Let us know what you think.