In 2011, the government challenged the construction industry to come up with a solution that would ensure new schools could be built quickly and without disrupting the day-to-day running of any existing schools, utilising a ‘kit-of-parts’ approach. Laing O’Rourke’s response is Project Sigma – a streamlined project solution tailor-made for the education sector. It is designed to combine Design for Manufacture and Assembly (DfMA) techniques with innovative digital engineering and utilising the latest innovations in component tracking for efficient builds. The result is a process that sees the majority of the school structure delivered using offsite manufactured components
Sigma is a prototype design that was developed as the next generation of precast concrete schools that Laing O’Rourke had previously delivered. The Priority Build Programme (PSBP), comprising seven builds across Yorkshire, is the first time that Sigma has been delivered in its entirety. Project leader Terry Williams explains: “Sigma had not been delivered before and therefore was effectively a prototype and it has worked. It means we can design and deliver a school within the accepted Government guidelines and assembled from a ‘kit-of-parts, all manufactured offsite.”
The various components
A typical classroom is 55 sq m and so, as Terry explains, “all seven schools are designed on variations of those dimensions.” The construction of the parts offsite is extensive and Terry lists what is manufactured before it even reaches the site. “Precast concrete sandwich panels, internal columns, including ‘C’ columns which also form vertical risers, precast ‘T’ beams carrying Bison hollowcore planks and SmartWall forming division walls and corridors are all delivered ready to be installed on site,” he says, adding: “In a very short period of time we can have a classroom built with the external wall finished, including windows pre-installed at the factory.” The ‘C’ columns facilitate the speedy installation of vertical MEP services without needing to create separate service risers. Other DfMA products incorporated in the overall design of the schools include twin-wall panels, precast parapets, Bison precast stairs, and MEP modules and pre-assembled modular roof-mounted plantrooms from Oldbury.
Speed is of the essence
“The benefits of using DfMA in the delivery of the schools are important because each one is built within the existing estate adjacent to live buildings," Terry says. “In addition to the programme benefits, this also means that we have to have fewer operatives on site. The Sigma model results in a significant reduction in the number of operatives required on site for the build compared to using in-situ methods.” The number of construction vehicle movements is also significantly reduced, again an important issue when operating within and around a live school environment.
And it wasn’t just the use of DfMA components that helped the Yorkshire Schools build increase efficiency, the use of a digital model was also important. “We utilised the 3D model excellently, particularly with component tracking” Terry says, “and for that I must credit Expanded’s operations manager Rob Auld. From day one we were calling off components from the factory through the model. Utilising the DE model, in real time, Rob and the project teams were able to predict any potential issues with sequence and delivery and through close coordination with EIP, ensure that the on site assembly continued seamlessly and without delay or disruption."
Having this 3D model meant that the team were able to prioritise different modules and components in order to keep the project moving along, even if one component had a problem. “The digital engineering function between sites and factory was excellent and really helped the progress.”
The next steps
“Three of our schools are now handed over and occupied and we’re working on their post-completion works which includes the demolition of the existing school buildings followed by hard and soft landscaping,” Terry says. “Three others – All Saints Catholic College, Whitcliffe Mount School and Carlton Bolling College – will be completed in August and September this year, with the final school – Oakbank School – due to finish in 2018.
The Sigma approach used for the programme so far has really benefited the delivery of quality and compliance, with factory standards of quality control being applied to major components such as external wall panels. This has resulted in a high standard of installation, which in turn has meant a reduction in the ongoing FM service charges for the schools, which are some of the lowest seen in comparison to similar education projects."