Timber Succeeds With Military Precision
As reported in previous issues of Structural Timber magazine, a huge MoD development scheme is currently taking place on Salisbury Plain using timber frame to house military personnel and their families. The final phase is nearing completion.
Salisbury Plain has long been associated with the British Army. Officially designated as Salisbury Plain Training Area (SPTA), it is the largest in the UK and is used by the regular army, reserve units, cadets and NATO allies. Stretching across 94,000 acres, the Training Area is also home to military personnel and their families.
As part of the Ministry of Defence's commitment to bring back Field Army units from Germany by 2020, an extra 4,300 service personnel and their families will relocate to their new home on Salisbury Plain in 2019/2020. To accommodate the additional residents, three new housing and community schemes - Bulford, Ludgershall and Larkhill, are being built on the Plain.
The £250million contract was awarded to Lovell, part of UK construction and regeneration group Morgan Sindall Group plc. The Defence Infrastructure Organisation tasked Lovell with delivering 917 homes - service families' accommodation (SFA) – over the three sites in a little over two years. To hit the May 2020 deadline, speed and accuracy
are crucial, therefore a form of offsite construction was a given.
To manage the delivery risk, Lovell awarded the construction of the properties to two timber frame providers, Taylor Lane Timber Frame and Stewart Milne Timber Systems
(SMTS). Taylor Lane was charged with completing 225 units at Bulford and SMTS, 242 units at Ludgershall. However, Larkhill is different. The Larkhill site comprises 450 units,
twice the size of the other two. So Lovell made a far-reaching decision for the two competing timber frame companies to work together on the one site, collaborating on all aspects of the build – a move which has been recognised as a pioneering move for UK housebuilding. As a consolidated solution was essential for delivering the build programme, Lovell required a willingness for both parties to collaborate at every level including design.
The companies worked with six basic house types, to streamline manufacturing and build efficiencies. Taylor Lane used its 140mm timber frame system with 75mm insulation to achieve the required U-value (0.21 W/m2K). Each property is designed to have an energy performance 19% greater than Building Regulations requirements. Several engineering solutions were designed in as a result of early planning meetings between Taylor Lane and SMTS, including avoiding stepped-in roofs where the step-in level was less than 150mm.
The two timber housing experts co-ordinated duct routes in floors, and eaves and verge details to ensure the same solution. Each company used its preferred joist manufacturer, but the depths were uniform. Both businesses also opted to erect the roof structures at ground level for fast-track delivery, enabling the roofs to be constructed ahead of/in conjunction with the ground and first floor frame, and minimise the risks associated with working at height.
Taylor Lane started by erecting 225 plots at Bulford, in just 29 weeks. Lovell had a strict handover programme which had to be met. Taylor Lane forecast when plots would be complete to allow planning for follow-on trades. This site set the standard for Taylor Lane, in both production output and operations. With erecting teams moving between the two timber frame providers, it was an opportunity for the erectors to learn the methods associated with the two systems and the layouts of the houses and sites. Taylor Lane handed over the final frame at Bulford on 30 November 2018.
Larkhill required dedicated onsite management and efficient programming. Its success has been reliant on exceptional communication. The Taylor Lane and SMTS site offices were opposite one another, with the site supervisors meeting daily to share crane plans, road closures, deliveries and delivery schedules to accommodate one other and not compromise the slew radius.
Initially, both companies handed over five units per week, this accelerated to a combined 16 units per week. This could not have been achieved with traditional masonry construction, the programme would have taken around five rather than two years to complete. This fasttrack, high-volume project is an industry exemplar, demonstrating the benefits of timber frame for speed, precision and efficiency. Taylor Lane celebrated the erection of its final unit at Larkhill – the last property of the contract – with a
topping out ceremony on 2 August.
With the final phase of the Army Basing Programme underway, military personnel have already begun the relocation to Salisbury Plain, occupying completed properties at Bulford and Ludgershall. Lovell is on track to complete the project in advance of the May 2020 deadline. "The rate of delivery achieved on our SPTA scheme is frankly incredible," says John Leary, Major Projects Director, Lovell. "As with our earlier scheme at MoD Stafford (2014/15), we have achieved productivity that is otherwise unprecedented in UK low rise housing, i.e. 16 units per week and much credit must be attributed to certain key ingredients of our supply chain, not least our two timber frame providers.
Taylor Lane and Stewart Milne Timber Systems were selected following rigorous qualitative scrutiny from a panel of the country's leading manufacturers/installers. "Given the demands of the client's programme, our decision to utilise OSM in the form of timber frame was instantly a given. From the onset our vison was to award one of the two smaller schemes to each of the two providers and allow their relative performance to be the route to our Larkhill decision. Both performed extremely well and were equally worthy of the larger site. Ultimately the leadership of to come to terms with. However, our partners persuaded us that with careful programming and planning the site could be safely compartmentalised to share the work equally and at the same time assure us of programme adherence.
"The results speak for themselves. I would have no hesitation in working with either or both of our timber frame partners on any future scheme, having immense confidence in their willingness to collaborate openly and with integrity and ultimately to deliver on their promise."