About The Project
Unlike Tesco’s previous retail projects, constructed with conventional built-up cladding system, the store in Barnstaple featured glulam timber and structural steel frame. It also used wall cassettes and, for the first time on a project of this scale, timber roof cassettes.
B&K Structures were responsible for delivering the structural frame, metal decking to the mezzanine together with the roof and wall cassette packages. The structural frame was designed and constructed using the ‘optimised hybrid’ concept.
Optimised hybrid means selecting the most effective combination of systems to meet the designer’s brief and performance specification. Hybrid structures offer bespoke solutions, incorporating the aesthetic and performance benefits associated with offsite manufactured solutions, delivering an optimised construction process.
The Brief
B&K Structures combined the environmental benefits of timber with the economic benefits of steel to create a unique hybrid structure for Tesco, ensuring an enhanced build time on site. Working with the main contractor, Bowmer & Kirkland, B&K Structures undertook the coordination of the design, supply and installation of the structural frame.
Having worked with the Tesco team on a number of projects (13 different stores to be exact), B&K Structures were able to liaise with the architect’s to develop a range of details such as the intricate connections for the glulam structure, which were formed with steel brackets and bolts. The main challenge with the project was co-ordinating the frame, roof and wall cassettes to ensure that all of the interfaces worked and the ambitious delivery programme was achieved. BIM modelling ensured the individual elements of the hybrid structure could be installed both accurately and efficiently.
The Solution
The project consisted of hybrid glulam timber, which created the main structural frame over the retail space, together with steel which was used for the mezzanine and ‘back of house’ areas. By removing the roof purlins, B&K Structures designed and installed 7,300m² of the prefabricated roof and wall cassettes, which enabled the application of internal and external finishes to be applied offsite, prior to arrival on site. This modern method of construction shortens the build time and on site labour costs, allowing the store to open earlier.
Both the roof and wall cassettes were designed as cladding elements and not to contribute to the overall stability of the structure. Despite this being the first time roof cassettes were used on such a scale, a faster build time was achieved and following a review of the build, a number of lessons were learnt that offered further programme enhancements for future projects.