Project Sevenoaks, United Kingdom


Piles to support residential apartments with 2-storey basement parking

Sector: Buildings

Piles were required to form a Contiguous Piled Wall for the development of residential apartments at London Road, Sevenoaks and to enable the 2-storey basement construction. 

Technical Specifications

Pile Type: CFA Secant Wall Piles

Number of Piles: 186no.         

Diameter: 750mm

Depth: 15m

The Challenge

Piles were required to form a Contiguous Piled Wall for the development of residential apartment at London Road, Sevenoaks and to enable the basement construction of up to 2-storeys in some areas. 

The prevailing ground conditions found within this area of Kent, meant that careful consideration is needed to ensure a design is developed that is both practical , in terms of achieving design depths through in to the sandstone and fulfills the requirement to permit a 2-storey basement excavation to be carried out in relative close proximity to neighbouring residences. 

The final design called for pile cages ranging between 9.0m and 15.0m in length. The longer pile cages meant that pre-fabricated cages were the preferred option for their intrinsic rigidity for placing through wet concrete. In addition, the concrete mix was adapted to increase workability and to ensure pile cage installation was achievable.  

The Solution

Using Franki Foundations' newly acquired Casagrande B175xp CFA rig, Franki installed 186no. 750mm dia. piles to 15.0m. A bespoke concrete mix was required for the CFA piling system as well as for surging up to 15.0m pile cages.

Franki were approached by the Client early on in their development process to provide guidance and advice on the practicalities of installing a piled wall at this site taking in to account the sloping nature of the site, the varied retained heights and the ground conditions which present its own set of specific considerations. 

With the benefit of a design development between parties, this scheme evolved from a fully temporarily propped retaining wall, to a combination of temporarily cantilevered, fully propped and in other areas; temporarily restrained by the use of a berm. This combination across the site was able to save money in the overall groundworks package as the propping scheme was reduced to the areas where the highest retained heights existed 

Project details

Project name





Secant Pile Wall, Continuous flight auger pile (CFA)

Contract type



Sevenoaks, United Kingdom

Building Period

2018 - 2018

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