The client required a more economical foundation solution to the expensive screw pile (installed to 25m depth) option they had been given.

The client had been quoted a time frame of 3 months for foundation installation but required a quicker option.

The foundations needed to be able to support the weight of six-storey precast concrete 87-apartment buildings.

The design had to achieve high design loads – both compression and tension.

The ground conditions were very soft clay, sand, and peat.

The project had to be cost effective or it would not be economical to proceed.

H5 treated Radiata Pine timber piles were determined as the best solution to be installed down to the founding layer.

The poles provided a flush foundation with no tie rods protruding which meant that pre-made steel cages could be easily installed rather than constructed on site.  This combined with rapid pole installation (only 3 weeks) meant that the overall construction programme was ahead of schedule by over 3 weeks.

Static Load Testing (tension) to 750 kN was carried out after installation was complete.

The foundation solution offered by NZGC cost approximately one-third of the original screw pile option.

The 35 tonne installation equipment required a 150mm thick layer of gravel to be laid over the site to support access.

Approximately 220 poles were installed for this project.