Piling isn’t a new technique for foundations, but it’s traditionally been used for large buildings where they support an unusually heavy load. Since the 1980s, though, the construction industry has come use it for everything from domestic conservatories to off-shore wind farms.
What Is Piling?
Piling is a type of deep foundation, used to transfer the load to a deeper level than is possible with a traditional shallow foundation. Vertical columns of concrete, steel or wood, or a combination, are driven deep into the ground to give extra support to the building that sits on top.
Traditionally piles were made of timber, but they’re now usually concrete, often reinforced or cased in steel. Positioned at regular intervals such as the intersections between walls, they’re driven down to denser, firmer levels, preventing either uplift or collapse and often linked by reinforced concrete ground beams, pile-caps or raft slabs.
When Is Piling Needed?
A traditional shallow foundation is enough when the ground is suitable and the load it has to support is moderate, but there are many ways for the ground to be unsuitable, so that piling is strongly advised.
- The water table is high.
- The soil is of a type whose stability will be affected by water.
- Deep trench foundations from a previous building would be too expensive to remove.
- Existing foundation trenches are unstable.
- The ground is unsuitable for more than two metres.
Driving the piles straight in, as opposed to shafts being excavated first, has the advantage that the process of driving compacts the soil around the pile, strengthening it and increasing its load-bearing capacity.
What Types of Piles Are Used?
Many different types of piles are used, but some are for specialist use, such as foundations in the sea-bed. The types commonly used for domestic building are:
- Sectional Augur Mini Piles — This versatile type, with either a hollow or a solid centre, is suitable for use on sites with limited access.
- Grout Injected Continuous Flight Auger —Grout is poured down the hollow centre to form the permanent column, and the big advantage is that it causes little noise or vibration.
- Steel Cased Bottom Driven Piles — Driving these from the bottom of the pile, instead of the top, means they don’t require heavy machinery, and can carry loads between 5 and 85 tonnes.
- Steel Cased Grundomat Driven Piles — Driven by an internal, compressed-air engine, these are ideal for light loads such as a conservatory in restricted areas, and cause very little vibration.
- Contiguous Piling — Ideal to create retaining walls, especially in basement construction.
All of these are ideal for specific conditions. If you aren’t sure which you might need, get in touch with our piling experts and we’ll be happy to advise you.