contiguous piling

Understanding Contiguous Piling: A Fundamental Technique In Foundation Engineering

In the realm of civil engineering and construction, foundation design plays a critical role in ensuring the stability and longevity of any structure. One indispensable technique in this domain is “contiguous piling.” Contiguous piling is a method used to create a continuous, interlocking barrier of piles, providing essential support for buildings and infrastructure projects. This blog post will delve into the significance, process, and benefits of contiguous piling.

What Is Contiguous Piling?

Contiguous piling, also known as secant piling, is a specialised foundation construction method used primarily in urban areas where space is limited. It involves the installation of closely spaced, overlapping concrete or steel piles to form a continuous wall around a construction site. The term “contiguous” refers to the piles’ close proximity, with minimal gaps between them.

The Contiguous Piling Process

1. Site Investigation: 

Before beginning the contiguous piling process, a thorough geotechnical site investigation is conducted. This step helps engineers understand the soil conditions, water table levels, and other factors that may influence the design and installation of the piles.

2. Pile Design: 

Based on the site investigation, engineers design the piles, taking into account factors such as the load-bearing capacity required, soil type, groundwater conditions, and any nearby structures that need protection during the construction process.

3. Pile Installation: 

The actual installation of contiguous piles can be achieved using various techniques, including:

   – Bored Piling: In this method, holes are drilled into the ground to the required depth, and then the piles are inserted into the holes, forming the contiguous wall.

   – Continuous Flight Auger (CFA) Piling: CFA piling involves drilling a hollow stem auger into the ground, which simultaneously removes the soil. Concrete is then pumped down the hollow stem, filling it as the auger is extracted, forming the piles.

   – Secant Piling: A variant of contiguous piling, secant piling involves the use of two types of piles – primary piles (usually concrete) and secondary piles (often reinforced with steel). The primary and secondary piles are alternated during installation, creating a more watertight and rigid wall.

4. Pile Interlocking: 

One of the significant advantages of contiguous piling is the interlocking feature. The piles are installed in such a way that they overlap, reducing the possibility of soil or water infiltration between the piles. This feature is particularly beneficial when constructing basements or underground structures in waterlogged areas.

5. Grouting: 

In some cases, after the piles are installed, grout (a mixture of cement and water) may be injected into the gaps between the piles. This process further enhances the waterproofing and structural integrity of the contiguous wall.


Contiguous piling is a fundamental technique in foundation engineering, offering numerous advantages for construction projects in urban areas with limited space and challenging soil conditions. By providing a secure and waterproof foundation, it ensures the longevity and stability of structures, promoting sustainable and reliable development in the built environment. As technology and construction practices continue to evolve, contiguous piling remains an invaluable tool for civil engineers and architects in their pursuit of innovative and lasting building solutions.