A proposed extension to a glass factory in Norwich was required to be constructed on piled foundations due to the presence of varying depths of fill below the proposed site.

We were tasked with providing the most economical solution for constructing the piled foundations. The final scheme consisted of suspended reinforced concrete slab over reinforced concrete ground beams supported on piles.

Due to the nature of the fill and underlying soils, which consisted of Norwich craig, where present, overlying chalk, the original proposal was to install 350mm diameter CFA piles to depths in excess of 20m using a 40Tonne piling rig to support the new structure. This suited the programme as installation time for the piles was 1 week.

However, on further examination of the nature of the fill, after we had carried out additional site investigation, a 600mm thick piling mat was required to support this type of piling rig. We re-examined the options available to construct the piles and by using a smaller 15Tonne piling rig the piling mat could be reduced to 300mm. Although the time to construct the piles extended to 3 weeks but when taking into account the time to construct the additional thickness of piling mat, and remove it from site on completion, there was no overall time increase in the overall programme and a material saving of around £30,000 resulted excluding the cost to remove and cart away piling mat material.

Due to the nature of the fill and underlying soils, which consisted of Norwich craig, where present, overlying chalk, the original proposal was to install 350mm diameter CFA piles to depths in excess of 20m using a 40Tonne piling rig to support the new structure. This suited the programme as installation time for the piles was 1 week.

It is important when considering piling costs on projects that in certain situations consideration of all aspects of the piling operation are taken into account not just the cost of the piles in isolation.

We will be pleased to advise on costings and programme times on similar contracts.