Background: In North London, a property faced a significant structural challenge. The existing wall, situated near trees, had been compromised due to the lateral pressure exerted by the trees’ roots. The threat of further damage or collapse necessitated a robust solution to support and reinforce the wall while considering the presence of the trees and potential ground movements.

Objective: The primary objective was to install a stable foundation system that could withstand the pressures exerted by the nearby trees, prevent future wall collapse, and accommodate potential ground heave or tree movement.

Solution: The solution proposed by Ground Sun involved the utilization of AB Chance screw pile foundations in conjunction with reinforced concrete (RC) ring beams. The square shaft screw piles were deemed ideal for providing reliable support in challenging soil conditions while minimizing disturbance to the tree roots.

Implementation:

  1. Site Assessment: A comprehensive site assessment was conducted to determine the extent of damage, soil conditions, and proximity of trees to the wall. This assessment guided the placement of screw piles to minimize disruption to the trees’ root systems.
  2. Foundation Design: The design incorporated square shaft screw piles, chosen for their load-bearing capacity and minimal environmental impact. Additionally, RC ring beams were designed to distribute the load evenly and provide lateral stability to the wall.
  3. Excavation: Careful excavation of 700mm deep pockets was undertaken by hand to identify suitable locations for pile installation, ensuring minimal disturbance to the surrounding trees’ root systems.
  4. Pile Installation: A small 1-ton, 750mm wide excavator was utilized for the installation of screw piles due to limited space availability. This equipment provided the necessary precision and manoeuvrability to navigate the site while minimizing disruption.
  5. Heave Protection: Heave protection boards were installed underneath the new wall to accommodate potential ground heave or tree movement, further enhancing the stability and longevity of the structure.