The National Gallery - Sunley Lightwell
About the Project
Westminster City Council had approved plans for an infill extension at the Grade I-listed National Gallery. The approved scheme, called the Accommodation Hub, involved creating additional space in the east ground floor of the main building, comprising of seven levels of office space and ancillary accommodation within the Sunley Lightwell. The works were adjacent to the existing Portrait Gallery and therefore noise and vibration needed to be at a minimum during the project’s duration.
The original presented scheme had larger diameter piles, but the applied loads could be carried more efficiently on a smaller diameter, deeper pile, with less volume of spoil to be removed, and therefore our alternative design was accepted, with 15nr 300mm diameter piles to depths of up to 21m installed, grouted using a site batched sand- cement grout mixed in a colloidal CX4/10 mixer.
Access to the site was the most significant challenge, with a 5 tonne limit accessing this central area of the National Gallery, the Hutte 203 rig needed to be stripped down of its mast, lowered into the existing basement on a 5 tonne gantry, and rebuilt in-situ. All material had to be brought in on pallets with a pallet truck, and all spoil removed in the same way, in single-use 1 tonne bags. Many of the piles encountered concrete obstructions, which had to be cored through using our tungsten carbide tipped cutting shoes. Despite these issues, noise and vibration from the piling works had no negative impact on the adjacent artwork and the project was finished on schedule.