Contractor Kajima UK Engineering has completed a 9250 m2, £11.5m Asda superstore in Swansea under a JCT81 contract. The project, completed in June, is based on Asda’s model store, which is a standard design modified to suit each site. The building has a steel frame structure with a standing-seam built-up roof, composite cladding and brickwork panel walls. The floor layout is based around a central open-plan sales area. A two-storey office and restaurant block is located in front of the sales area, with a warehouse and plant area at the rear.
The Swansea project made a cost saving of 5.75% on a similar Asda store built in Gateshead 18 months earlier. This gives the store a benchmark score of 65% on the government’s key performance indicator for construction costs, which means it is 15% better than the industry average (50%) for all projects.
The store was completed in 15 weeks, 39% faster than the Gateshead store. This gives it an 85% score on the indicator for construction time – 35% better than the industry average.
Kajima used modular units to speed up construction time.
Efficiency was improved by performance monitoring. Site processes were analysed to assess how much time was spent on productive and non-productive activities.
Asda has planned workshops with design team members and subcontractors to discuss what should be carried forward from this project.
How modularisation cut build time
“Asda was looking to make a quantum leap in the construction process,” says Richard Nicholls, the retailer’s store development manager. “The project aim was to bring down construction time without compromising safety or increasing costs, while producing a replicable build process that could be carried forward to the next project.” Asda has a standard store model that is adapted to suit each site. It also uses a set of partnering contractors and consultants to achieve year-on-year savings of 20% for store construction time and 10% in store costs. But to facilitate its “quantum leap”, Asda appointed Kajima, a contractor not included on its partnering list. The lessons learned from previous projects were made available to Kajima. The store was constructed in 15 weeks, following the completion of enabling works. This compared with the 26 weeks taken to construct a similar sized store in Gateshead 18 months earlier.
Cutting construction time means that more activities have to be carried out at the same time. Kajima proposed several changes to Asda’s standard construction model, including using modularisation to speed up the build time and to take activities off the critical path.
At the front of the store, on either side of the main entrance, are the double-storey office and restaurant. Kajima modularised these by bringing them to site as 28 fully fitted-out modules, taking them off the critical path. However, installing the units proved to be more difficult than the team had anticipated. “It was an experiment,” says Neil Sargent, Kajima’s contracts manager.
“Ultimately, if you are looking to bring down construction time, you have to start taking work off site. The lessons learned from this will be applied to future projects.”
Modular construction was also used in other parts of the building. Kajima clad the first 3 m of the external facade using modularised, brick-faced panels rather than building brick walls in situ. “The wall was constructed in February,” says Sargent.
“By using wall panels we took weather dependency out of the operation.” The panels also meant the mess associated with a wet trade such as brick-laying was avoided, and there was no need to have scaffolding around the outside of the building, freeing up space on site.
Kajima also used modularisation for the mechanical, refrigeration and electrical plantrooms. These were supplied as packaged units, fully assembled and commissioned, and installed in a separate area at the rear of the building. By mounting the units separate to the main store, Kajima ensured that they, too, remained clear of the critical path.
Kajima reduced construction time further by opting for single-span steelwork rafters above the sales floor instead of the complicated “steel tree” system of supporting columns Asda usually uses. Although the rafters were slightly more expensive, they were twice as quick to install. This meant the roof was made watertight earlier in the programme, giving an earlier start to other trades. Removing the columns also increased the flexibility of the sales floor layout and simplified floor tiling.
For the roof, Kajima used a structural lining tray rather than Asda’s usual purlins. The lining tray was installed from “up-lift” vehicles, which dispensed with the necessity to install safety netting below. Because the tray is strong enough to be walked on, this also meant the rolled standing-seam roofing could be installed without additional temporary supports.
The final major alteration to the standard store model involved creating a 2.1 × 1.5 m pipe-duct below the sales floor to carry refrigeration pipework to the chilled display units. Asda’s model method involved creating a 600 × 600 mm trench in the sales floor, which took the pipework installation off the critical path.
Dispensing with the trench also simplified the floor tile installation, and resolved the problem of having to have an open duct running across the sales floor during the fit-out stages. It also made it easier for Asda to incorporate late changes in the shop-floor layout.
How monitoring improved productivity
One area targeted for improvement by Asda was site productivity. “We wanted to know where we could do better,” says Mike Abel, Asda’s general manager of research and development.
Asda used Calibre, the Building Research Establishment’s site performance monitoring system, to measure who was doing what, how much time they were taking, how much their activity contributed to advancing the project and how much time was spent on non-productive activities. All site operatives were given an identifying number to wear on their vest, allowing the two BRE observers to record who was doing what task, and the time it took to do them.
To ensure communication between the trades, Kajima insisted on meeting in a “huddle” every morning and evening. The idea was borrowed from Asda’s management team, and was seen as a chance to sort out problems.
At Swansea, the results of the previous day’s Calibre monitoring were reviewed by the contractors and subcontractors at the morning huddle. The aim was not to look at what went wrong but at how the process could be improved the next day. For example, Calibre showed that the productivity of the lining contractors had decreased. At the huddle, the problem was found to have been caused by ductwork stored on site, which was restricting the liners’ access.
Calibre showed that the Swansea team spent 8% more time on productive activities than the industry maximum from previously monitored sites. The lower figures at the start of the project were caused by the high number of managers on site relative to the number of operatives.
Neil Sargent, Kajima’s contracts manager, thinks the high productivity figure was caused by a change in the attitude of everyone working on the project – something that was targeted before the project was on site.
Even before Kajima had been awarded the contract, it arranged a three-day workshop with its selected subcontractors and Asda’s team. This was to develop the process through which the project objectives would be achieved. These objectives included building the store in less than 20 weeks, and for 10% less than a similar store built a year earlier.
Before starting on site, Kajima gave all its subcontractors an induction to explain how the teamwork culture would work and to allow them to commit to delivering the objectives. Sargent describes this as “creating the atmosphere to allow operatives to challenge the obvious, to try to think outside their particular box and to think of others”.
Colin Gray is head of the University of Reading’s Department of Construction Management and EngineeringThis store was constructed at a speed comparable with the best in the industry. The benefit of design and build in this instance is the ability to respond to the “big targets” set by the client. Setting sufficiently big targets predisposes the team to a radical review of all processes. It is a crude but effective method of challenging existing practice. Three areas of existing practice were changed simultaneously to achieve this level of performance. The principles of buildability were applied throughout. Where possible, activities were moved off site or the design was changed to remove work or allow parallel working. Despite the use of large-scale prefabrication of elements, the overall cost was cut. It would be interesting to see where the trade-offs between higher unit costs and production efficiency arose. The organisation of the project, through design and build, enabled the design and construction implications of each alternative to be evaluated. In the past, only construction management projects have reported this level of integrated review. Also, it is rare for the contractor to take control of the integration of the subcontractors. Even the best trade contractors find it difficult to manage their own work as well as the integration between packages.
Martyn Jones is principal lecturer in construction management at the Faculty of the Built Environment at the University of the West of EnglandAnother project from the retail sector has demonstrated that step improvements can be achieved given the right team and project environment. Innovations in design, manufacture, assembly, and management of the project’s key supply chains allowed Kajima to reshape both product and process. This reduced build time by taking critical tasks off site or removing them from the critical path. Kajima’s approach depended on complementary innovations to tackle the “soft” issues associated with improvement, such as developing greater customer focus. This involved Kajima working upstream with Asda to determine what it means by value, making this more explicit, and then communicating it downstream to the specialist contractors. By being more aware of Asda’s needs, Kajima helped to create the conditions that allowed it to release more of its potential to deliver even greater value for the client. As a regular client, Asda has recognised the importance of recording the lessons learned on this project for the benefit of all its construction partners, and as a springboard for further improvements in future projects – a key part of a strategy of continuous improvement.
John Connaughton is a partner at Davis Langdon Consultancy and is chair of the Innovation and Research committee of the Construction Industry CouncilIt will be interesting to see how Wal-Mart’s bid for Asda affects its approach to construction. Wal-Mart has a near-legendary reputation in the USA for developing the leanest of supply chains and for driving suppliers’ costs and margins down with the promise of access to massive sales volumes. At Swansea, it seems that Asda’s contractor, Kajima, had a brief to deliver a radical change in performance. The reported time and cost savings are impressive, and it is good to see the use of modularisation, monitoring of site productivity, teambuilding and learning through post-hoc evaluation. For me, though, the real interest is the relationship between client and contractor, in particular the freedom given to the contractor to search creatively for genuine improvement. The design modifications made to the roof and the sales-floor pipe trench are examples of what we at DL&E call “benefit trading”, a process whereby both parties to a deal gain by trading benefits that each is uniquely placed to identify. We hope Asda continues to seek improvement through such a positive and creative use of the skill and expertise available in the design and construction team.
Changing attitudesAsda selected Kajima because of its philosophy that the client gets what the client wants. Bob Simpson, Asda’s head of development, says: “They brought a retail philosophy to construction. Their approach was, ‘If we have a problem with the client, we must have misunderstood the client’.” Kajima questioned everything in an attempt “to understand what Asda’s requirements were and how Asda worked”, says Simpson. “They asked, does the client understand the ramifications of its specification, for example, the use of columns on the sales floor?”
What happens next?Following the store’s completion, Asda plans to hold several debriefing sessions with the contractor and subcontractors to discuss which aspects of the project worked, which did not work, and how the construction process could be altered to incorporate changes. Asda’s other partnering contractors have visited the site and the lessons learned will be incorporated into future projects. “What Asda has learned from this project is that I don’t think we can go on as we have been,” says Bob Simpson.
Client Asda Architect Dewjoc Main Contractor Kajima UK Engineering Cost Manager Cullum Morris Powles Structural Engineer HJT Services Engineer Dave Dickinson & Associates Services Contractor Elequip Cladding Contractor Lakesmere Cladding Steelwork Fabrication and Erection Severfield Reeve