All Foundations were contracted to provide foundation piles to support a 7.5m deep sub-basement extension to the former Royal Sun Alliance Headquarters, Selwyn House, next to Green Park in London which is now a single residence.
Due to the location of the building Ian Cull, our Senior Estimator for the Southern division of All Foundations, visited the site to determine the available access and concluded that Restricted Access piling would be required due to the very tight restrictions both on the site and in the surrounding area.
The challenge was to design and install piles to support compressive loads of between 300-700KN and tension loads of 325KN. The ground conditions being water bearing sand and gravel to a depth of 11.0m, overlying London Clay. The working area being 12m x 10m, set 3.0m below pavement level. The site being in a high security area adjacent to St James’ Palace and Clarence House, with a very narrow access road surrounding the building.
Due to the confines of the site, Engel Construction originally envisaged the need to erect a crane to lift the piling rig and equipment into the basement area.
The solution put forward by All Foundations, and subsequently accepted, was to design and install, 450mm diameter x 22.5m deep, SFA (Segmental Flight Auger) piles using our Klemm 702 min rig, with the rig and equipment being lifted into the basement using our 15T capacity Hiab wagon, hence making substantial savings against potential crane hire. The contract value agreed at £80k over a 5 week period.
As Ian was acutely aware of the site conditions and issues which could, if not managed properly, create problems, he worked very closely with the both the All Foundations and Engel Construction projects team to ensure that all potential issues were proactively researched and neutralised where possible.
Due to our proactive approach, experienced site personnel and equipment we were able to complete the piling work on time and within budget. Much to the delight of Derek Corcoran, Project Manager for Engel, who had this to say:
‘We nominated All Foundations for piling works at our Selwyn House project. The site was very tight and the preplanning had to be accurate so as not to cause delays to the project and traffic problems on the street outside when we the piling team were mobilising. All Foundations compiled a plan for this and executed it well. Once mobilised the piling team got started and we in what were tight difficult conditions. We encountered some obstacles along the way you do in every job but the team were positive and proactive in overcoming any problems and had foresight to eliminate other problems we could have encountered. We had overall good experience working with All Foundations and would not hesitate to work with them for future similar project.’
We are proud to have been able to exceed Engel Constructions expectations, and even though the site was very small, with extremely difficult access restrictions, we were able to complete the works on time. This is solely down to the work ethic and dedication of the professional, experienced project team and site personnel.