Tree & Root Areas – Non-Invasive, Displacement Piling System

Ground Sun designed, supplied and installed in excess of 50 piles for the new structures in this Horatio’s Garden project at Stanmore Orthopaedic Hospital.


Horatio’s Garden is a national charity creating and nurturing beautiful gardens in NHS spinal injury centres. The gardens provide a fully accessible space enabling spinal cord injury patients to spend time surrounded by natural elements.

The new structures consisted of 3 garden pods, a garden room and a gardener’s area.

The garden is surrounded by protected trees in a root protection zone. The AB Chance helical screw piles system was ideal as it is a non-invasive, displacement piling system with no damage to tree roots. The geology is London Clay which is well known for its high plasticity. This can make it susceptible to moisture movement, swelling or contraction, leading to heave or subsidence. Traditional trench foundations would therefore be difficult to build on as it would be susceptible to movement.

The piles were installed over a 4 day period using a 5 tonne excavator. No piling mats were required and no excavation spoil to remove.

Up to 400kN ultimate capacity loads were required. A combination of SS5 and SS150 AB Chance helical piles were used.

A 160mm sulphate resistant C30 grout column provided additional protection for the pile and meant the screw piles were friction piles as well as end-bearing.