The Worst Types of Soils for Piling

Deep foundation piling is the process of installing ‘piles’ – long stilts made of wood, concrete, or steel – in the ground to form the foundations for a construction above. Piling has been around since ancient times and takes advantage of denser, tougher earth at greater depths. The piles bypass the softer, more easily shiftable earth on the upper levels and rest on the much firmer levels below. The softer earth around the piles helps brace the foundations in place while the end rests on the firmest surface, providing a solid foundation for the construction to take place on!

There are many different types and compositions of earth. Soil can be high in sand, or clay. It may have a lot of rocks buried within it or be waterlogged from poor drainage. These variations can have a huge effect on the stability and strength of foundations. Let’s take a quick look at some of the worst variations and how these can affect your foundations.


Peat is a fine deposit made up of a mixture of soil and decomposed vegetation, and can be found in wetlands like peatlands, moors, and bogs etc. Peat absorbs and holds moisture very well and can make a fairly firm surface when damp and compressed. However, peat dries out completely to become crisp and fragile, and even poses a huge fire risk when dry. These factors make it unsuitable for piling.


Silt is another fine grainy deposit, similar to peat, but mineral in origin. Silt stores water too effectively, making draining difficult, and the material expands as it absorbs moisture which would cause warping and erosion, making it an unsuitable material to set foundations in.


Clay is a dense material most famous for its use in pottery, fired clay provides us with plates, flower vases, and a whole range of other products! Clay, like silt, expands significantly when it absorbs moisture, while also becoming soft and malleable. Because of this constant expansion and contraction, clay would likely cause cracks to appear in foundations over time, meaning it’s a poor material to install your piles in!

Sand and Gravel

Soil with high concentrations of sand or gravel tend to drain moisture away very easily due to the gaps between the large grains. If compacted well and kept contained these surfaces can be used to support deep foundation piling, but if there is a flow of liquid nearby, the particles or sand or stone can be washed away from underneath, leaving gaps in your foundations. Sandy and gravely soils are best avoided if possible.

All construction projects must begin with the most important decision – the foundations. The foundations provide the base for the rest of your construction and must be completed to the highest standards and with utmost expertise. Here at Rhino Piling we have over a century of collective experience in foundation piling and start every project with a full on-site evaluation. Get in touch today to see what we can do for you!