Value engineering trimmed costs to meet budget constraints while the use of BIM provided legacy lessons on Woodlands School in Basildon.
Project: Woodlands School Basildon
Client: Essex County Council/Essex LEP
Contract value: £26.5m
Main contractor: Skanska
Architect: Nicholas Hare Architects
Start date: April 2012
Completion date: January 2014
The government’s cancellation of the Building Schools for the Future programme in July 2010 saw billions of pounds of potential work stripped away from contractors.
Overnight plans to rebuild thousands of schools across the country were shelved and the construction industry was left doing its sums.
One contractor in particular might have felt more aggrieved than most over education secretary Michael Gove’s decision.
First in, last out
Skanska has been involved in the BSF programme from day one. It had taken the ‘pathfinder’ deal to build schools in Bristol, won a similar deal for Essex schools and is well versed on the delivery of BSF schemes.
And with the closure of the programme it is perhaps fitting the contractor that was one of its leading lights is involved on one of the Essex BSF’s final projects.
The Woodlands School in Basildon suffers from ageing facilities that are costly to run and pricey to repair.
But under a £25m deal, Skanska will be delivering a raft of completely new facilities for the school’s 1,500 pupils. The project’s 90-week build programme should see the school ready for staff and pupils to move into at the beginning of 2014.
Trimming the costs
It’s been a long time coming for a scheme that was initially given the all clear in 2010. Since then it has gone through various stages of design and redesign until financial close was finally reached in spring last year.
“It was initially thought the school would cost around £30m, but in fairness that level of funding just wasn’t there”
Ian Shinn, Skanska
“It was initially thought the school would cost around £30m, but in fairness that level of funding just wasn’t there,” says Skanska project manager Ian Shinn.
“With help from the client and the rest of the project team, there has been some redesign and value engineering to help trim that down to the £26.5m we are looking at now.”
Simple but affordable design
By keeping the design simple and working to governmental guidelines on school building, the team managed to drive the cost down, enabling the project to go ahead.
The new school buildings comprise two teaching wings linked by a central entrance atrium with library, sports hall, offices and art space. Plant space is provided on the roof and there are ancillary buildings that include the boiler house for the two gas boilers and heat exchangers.
“Initially there were plans to install a biomass boiler, but that was replaced by two gas boilers during the value-engineering process,” Mr Shinn says.
From Outstanding to Very Good
In fact, the bulk of the new school’s energy-efficiency targets will be met thanks to its tight insulation and efficient local environment control through the building management system.
Initially expected to hit the BREEAM Outstanding benchmark for sustainable building, that target has been revised down to Very Good.
The site itself, separated from the existing live school buildings by a hoarding that runs around the new build, falls away across the schools footprint and has been subject to a cut-and-fill regime that in some areas sees formation level stand the best part of 2 m above the surrounding football and rugby pitches.
“Lime stabilisation and treatment of the existing, excavated clay would have hit the budget. It’s tight here anyway so muck-away was the only real option”
Ian Shinn, Skanska
Fill has been imported thanks to the unsuitability of the excavated clay, which would have taken too long to process into useable fill.
“It was a time and cost constraint issue as much as anything,” Mr Shinn explains, adding: “Lime stabilisation and treatment of the existing, excavated clay would have hit the budget. It’s tight here anyway, so muck-away was the only real option.”
A raft of 450 mm-diameter CFA piles have been driven 18 m into the earth, with beams and pile caps supplementing ground-bearing and suspended ground-floor slabs at around 250 mm deep.
The structure itself is steel-framed and designed to be as lightweight as possible, with two floors in the teaching wings and a large single-floor central atrium.
Precast concrete planks have been used for the floor slabs and will be left as exposed soffits with Metsec-framed external walls and glazed curtain walls. These will be clad with timber, Trespa and brick cladding systems, while the roof will be covered in a mixture of Permaquick membrane and Kalzip metal roofing systems.
Critical path tweaks
By tweaking the design, the team managed to speed up the construction process by moving the cladding process off the critical path, enabling the mechanical and electrical work to start much more quickly.
By installing the metal framing system outside the structural frame itself, the team has been able to get the building weathertight earlier.
“The wet trades suffered because of the weather, so we took the cladding off the critical path and changed the sequence of the build,” Mr Shinn explains.
“Traditionally you would finish and paint the walls, soffit and bulkhead before getting the services in and putting in the doors and joinery. Here the finishes are being completed last, which means we can pull the commissioning period in a little earlier.”
Putting the emphasis on the services side makes sense, as it means the team has already made a start on the commission process and proven the capability of the building management system.
“There is 10 weeks of commissioning,” says Skanska services project manager Daren Mansford. “It means we can start everything earlier.”
Rapid prefabricated services
Service runs along the corridors, prefabricated at Skanska’s facility in Slough, have allowed the team to complete a corridor in just two days.
Brought to site in sections, the service pods are lifted onto each floor at a designated point before being fixed in position. The heavy building information modelling ethos on the scheme (see box) ensures there are no clashes and that everything has been placed and called off in perfect sequence.
With just six months before the project is handed over to the client, Mr Shinn is quick to praise the relationship built up between the site team, client and the school itself.
“It has been really important,” he says. “They have understood the difficulties we have had and also we understand that it is important that the area gets the facility it deserves.”
Come January 2014, the Basildon community will get just that and Skanska will bring the curtain down on its Essex BSF education.
School teaches Skanska BIM lesson
The Skanska team is using the project to help prove to the rest of the business just how important the full integration of building information modelling systems is.
“The plan is to use what we learn from this project as a BIM exemplar and run those findings across the rest of the company,” says Skanska BIM coordinator Alex Gibson.
Although not quite the perfect project – it came a little late for its full BIM credentials to be completely examined, according to Mr Gibson – the team has used it to focus on the benefits brought from 3D modelling and the level of information that can be passed through from the construction phase to the facilities management team.
“We missed the opportunity to get on board at the beginning of the project,” Mr Gibson says. “We were in at the tail-end of the detailed design.”
For the construction team the benefits are obvious, with clash detection and defect management top of Mr Shinn’s list.
“It saves time and allows us to examine any problems on a computer screen,” he says. “It can help prevent us losing any money and really means we can get instant information over to our subcontractors.”
The supply chain has also bought into the concept. Each has a tablet computer that enables defects to be photographed and sent directly to those concerned. This has seen any defects closed out quickly and efficiently.
But the BIM benefits will also help Skanska’s facilities management arm when it takes over the maintenance of the school upon handover.
“We have had the FM team involved early on,” Mr Gibson explains. “They are working closely with us and are able to drill down through the detail. There really will be a great benefit for those involved in the legacy side of the building.”