What is piling in construction?
piling is the process of installing by boring long, strong columns called piles into the ground to support structures when the surface soil is too weak to bear the load. These piles transfer the weight of the building, bridge, or other structure to deeper, more stable soil or rock layers, preventing settlement, tilting, or structural failure.
Piling prepares the ground to carry heavy loads, such as a new skyscrapers, big buildings, road or another piece of infrastructure.
What are pile foundations?
Pile foundations are a type of deep foundation used in construction to support structures when the surface soil is too weak or unstable to carry the load safely. They consist of long, slender columns called piles that are driven, drilled, or pressed deep into the ground to transfer the building’s weight to stronger soil or rock layers below.
Pile foundations consist of long, slender elements, usually made from steel or reinforced concrete, designed to transfer structural loads from weak, compressible soils down to stronger, more stable soil or rock layers at greater depths. By reaching these firmer layers, pile foundations provide a solid and reliable base for construction projects.
It is important to distinguish between a pile and a pile foundation, as they serve related but distinct roles. A pile is the individual column that carries the load down into the soil, while a pile foundation refers to the complete system of multiple piles that together form a stable base to support the structure.
Key Points about Pile Foundations:
Purpose: Provide stability, prevent settlement, and support heavy loads.
Materials: Usually made of concrete, steel, timber, or composite materials.
- Types of Piles:
- End-bearing piles: Transfer the load directly to strong soil or rock.
- Friction piles: Transfer load through friction along the pile shaft in weak soil.
When to use piling foundations in construction
Pile foundations are used to provide a safe and stable base for structures, especially in challenging ground conditions. They are particularly important in the following scenarios:
- When the groundwater level is high, making shallow foundations impractical
- When the structure carries heavy loads that require extra support
- When other foundation types are either too expensive or unsuitable
- When the soil near the surface is soft or highly compressible
- When the site is prone to scouring, such as near rivers or along the seashore
- When there are nearby canals, deep drainage systems, or other underground obstacles
- When it is not possible to excavate to the required depth due to weak soil
- When keeping foundation trenches dry is difficult, even with pumping or other methods
What are the types of piling?
The two primary types of piling are end-bearing piles and friction piles:
End-bearing piles
End-bearing piles are piles that transfer the load of a structure directly to a strong soil or rock layer located deep below the ground. The pile acts like a column, carrying the building’s weight straight to a firm layer that can safely support it.
Friction piles
Friction piles are deep foundation elements that transfer the load of a structure to the surrounding soil along the entire length of the pile, rather than relying on a solid layer at the tip. The load is carried through skin friction between the pile surface and the soil.
These piling methods are defined by how they support the structure, either by reaching a solid layer beneath the ground or by generating friction along the pile shaft.
In the following section, we will explore the main types of pile foundations. Each type can use end-bearing piles, friction piles, or a combination of both, depending on the soil conditions and the specific needs of the project.
Types of pile foundation work
Pile foundations come in various types and subcategories, each designed to suit specific soil conditions, load requirements, and project needs.
1. main Pile Foundation Types (installation-based) include:
- Driven piles
- Bored piles
- cast-in-situ piles
2. Subtypes of Bored Piles:
These are not separate foundation systems — they fall under bored piles:
- Rotary bored piling — a drilling technique
- Continuous Flight Auger (CFA) piles — another drilling technique
both are just methods used to install bored piles, not standalone foundation types.
3. Pile Types by Material
These describe the material of the pile, not the foundation system:
- Steel piles
- Concrete piles
- Timber piles
- Sheet piles
(Sheet piles — only used for shoring for retaining walls and excavation support, not foundations)
While the construction methods differ for each type, they all share the common feature of being either driven or drilled into the ground to provide a stable foundation. Continue reading to learn more about each type, or use the links above to navigate directly to a specific pile foundation.
Methods of constructing piles
Driven pile foundations
Driven piles are long, strong columns made of timber, concrete, or steel that are driven into the ground using heavy machinery to create a stable foundation for buildings and structures.
Driven piles are piles that are installed by hammering or vibrating them into the ground without drilling a hole first. They rely on displacement, meaning they push the soil aside as they go down, which helps increase soil density and improve the foundation’s load-bearing capacity.
Bored pile foundations
Bored piles are concrete piles made by drilling first instead of hammering, making them ideal for sites where noise, vibration, or soil displacement must be minimized.
Bored piles are deep foundation elements formed by drilling a hole into the ground and then filling it with concrete, usually with a steel reinforcement cage inside. Unlike driven piles, they do not displace the soil; instead, the soil is removed and replaced with concrete.
Driven and cast in-situ piles
They are hollow tubes driven into the ground, then filled with concrete to create a strong, custom-formed pile.
Driven and cast in-situ piles are piles that are driven into the ground first as a hollow casing, and then filled with concrete on site to form the final pile. This method combines the advantages of driven piles (good soil compaction and capacity) with the flexibility of casting concrete in place.
Driven and cast in-situ piles combine the benefits of both driven pile installation and cast-in-place concrete piling.
One common approach uses a permanent casing. In this method, a thin, corrugated steel tube is driven into the ground with the help of a mandrel inside the casing. After reaching the required depth, the mandrel is removed while the casing remains in place. Concrete is then poured into the casing, creating a composite pile made from both steel and concrete.
Another variation uses a temporary casing, often known as the Franki method. Here, a steel reinforcement cage is lowered into the hollow casing. As dry concrete mix is added and compacted, the casing is gradually withdrawn. The pressure forces some of the concrete out of the bottom, forming an enlarged base or bulb that significantly increases the pile’s load-bearing capacity.
Rotary bored piling
It is a technique for creating deep foundations by rotating a drill to excavate soil, allowing the pile to reach strong soil or rock layers without causing much vibration or noise.
Rotary bored piling is a method of constructing bored piles by using a rotary drilling rig to drill a deep hole into the ground, which is then filled with concrete and usually reinforced with steel.
Continuous Flight Auger (CFA) piles
CFA piles are concrete piles made on-site without removing the soil, using a continuous auger to drill and place the concrete in one operation. This method is quiet, low-vibration, and ideal for urban construction.
CFA piles, or Continuous Flight Auger piles also known as auger cast piling, are a type of bored pile constructed by drilling into the ground with a hollow stem auger while simultaneously pumping concrete through the auger as it is withdrawn. A steel reinforcement cage is then inserted into the fresh concrete.
Pile Types by Material:
Steel piles
Steel piles are long steel columns driven or pressed into the ground to transfer structural loads to deeper, stronger soil or rock layers.
Steel piles are pile foundations made from steel, used to support structures where strong, durable, and high-capacity piles are required. They are often used in deep foundations, heavy structures, or challenging soil conditions.
Concrete piles
Concrete piles are long, strong columns of concrete (sometimes reinforced with steel) that are installed into the ground to support buildings, bridges, and other structures.
Concrete piles are pile foundations made from concrete, used to transfer loads from structures to deeper, stronger soil or rock layers. They can be precast off-site or cast-in-situ on site, depending on the project requirements.
Timber piles
Timber piles are wooden posts that transfer the load of a building or structure to deeper, more stable soil layers.
Timber piles are long wooden columns driven into the ground to provide support for structures, especially where the soil is soft or weak. They are one of the oldest types of pile foundations and are still used today for certain applications.
Sheet piles
Sheet piles create a barrier in the ground by connecting multiple panels side by side, providing support and preventing soil or water from moving.
Sheet piles are long, flat panels with interlocking edges that are driven into the ground to form a continuous wall. They are primarily used to retain soil or water, making them ideal for retaining walls, cofferdams, coastal protection, and underground structures.
Factors That Determine the best Piling Method
When choosing the best piling method, engineers look at a few key factors. First, they assess the soil conditions to understand its strength, depth of firm layers, and groundwater levels. Then they consider the load the structure will carry and match it with a pile type that can safely support it. Site constraints also matter—areas with limited space or strict noise and vibration limits may require bored or CFA piles. Engineers also evaluate environmental conditions, access for equipment, and overall project budget and timeline. By reviewing these points, they select the piling method that provides the safest and most practical foundation for the project.
Additional factors engineers may consider:
not just that but the engineers also need to examine a range of factors, including:
- Groundwater control needs: Whether dewatering is required or whether the piling method works well in high-water-table conditions.
- Environmental impact: Soil contamination, vibration limits, noise restrictions, and impact on nearby structures or utilities.
- Durability requirements: Corrosion risk for steel piles, sulphate attack on concrete, or long-term performance in marine environments.
- Pile spacing and layout: Some methods require more room or precise alignment, which can affect the choice.
- Construction speed: Some methods like CFA piles are faster, while rotary bored piles may take longer.
- Load distribution: Whether the structure requires end-bearing, friction, or a combination of both.
- The depth of the excavation
- The angle at which the pile needs to be installed
- The environmental issues that impact local residents
Need a strong and reliable foundation? Contact with our piling experts at KON today for a personalized solution or Get a Quote today about you project today.