A deep foundation is a type of foundation that transfers building loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths. A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the ground at the building site.

(a) Classification based on L/d ratio –

• Short Pile (when L/d ratio is <= 10)
• Long Pile (when L/d ratio is > 10)

(b) Classification based on angle of Inclination –

• Vertical Piles (generally to carry vertical loads)
• Batter or Raker Piles (to carry lateral loads)

(c) Classification based on load transfer –

• End bearing Piles (transmit load through bottom tips) also known as Point bearing Piles
• Friction Piles (load is transfer through skin friction between embedded surface of pile and surrounding soil) also termed as Floating Piles
• Combined end bearing and friction Piles (load is transfer through both bottom tips, and skin friction between embedded surface of pile and surrounding soil, that is why it is termed as Combined Piles)

(d) Classification based on Composition –

• Steel Piles (generally load taken upto 400 kN to 1200 kN)
• Timber Piles (generally load taken upto 250 kN)
• Concrete / RCC Piles (pre-stressed pile may take load upto 2000 kN and pre-cast pile may take load upto 1000 kN)
• Composite Piles (upper portion is made up of concrete and lower portion is made up of either timber or steel. difficult to provide a proper joint)
• Sand Piles (bored holes are filled with sand, compacted and covered with concrete cap at the top)

(e) Classification based on method of installation –

• Driven Piles (driven into soil by applying blows from the top)
• Cast-in-situ Piles (hole driven into the ground and then material poured)
• Driven and cast-in-situ Piles (form by driving the casing (closed form bottom end) into ground then filling the material into it and also casing may or may not be removed/ withdrawn after filling the material)

(f) Classification based on use –

These are however classified according to the usage of piles.

• Load bearing Piles
• Tension Piles
• Sheet Piles
• Compaction Piles
• Anchor Piles
• Fender Piles