The infamous psychiatric hospital is undergoing a comprehensive redevelopment for which Kier has employed extensive BIM design and offsite construction.
Project: Broadmoor Hospital Redevelopment
Client: West London Mental Health NHS Trust
Contract value: £115m
Main contractor: Kier
Architect: Oxford Architects
Precast manufacturers: Techrete, Bison, McCann, Prefaxis
Start date: January 2014
Completion date: February 2020
Throughout its century and a half history, Broadmoor Hospital has been associated with some of the most dangerous criminals in Britain.
The Berkshire psychiatric facility dates back to 1863, and most of the in-use buildings on the estate date from the Victorian era.
That will soon change. In 2009, the West London Mental Health NHS Trust, which has operated Broadmoor since 2001, began planning a comprehensive redevelopment of the site, which involves transferring almost the entirety of the hospital’s operations into new clinical facilities.
The design was approved by planners in 2012 and Kier was awarded the £115m construction contract, starting on site in January 2014.
Given the sensitive nature of Broadmoor, the trust was keen to appoint a builder that would maximise the use of offsite technology and therefore minimise the construction impact on the live hospital.
Contractor experience vital
Oxford Architects designed the redevelopment – but only to RIBA stage D, as the trust was keen to bring in a contractor’s buildability expertise at that point.
“One key reason why Kier was awarded the contract is that we were the only bidder to offer a precast concrete solution for the building frames”
Steve Giles, Kier
“They wanted an experienced contractor who would use BIM and modern methods of construction,” says Kier senior project manager Steve Giles. “One key reason why Kier was awarded the contract is that we were the only bidder to offer a precast concrete solution for the building frames.
“We had delivered a £200m prison in Wolverhampton using this precast model and it gave the trust confidence in our ability to deliver.”
Just over two years ago, the Department of Health approved a £242m redevelopment of Broadmoor Hospital.
It has been working with Kier to oversee completion of the new 234-bed hospital, set to open in the spring of 2017.
In September 2015, the new clinical model of care was presented to the West London Mental Health NHS Trust’s Quality Committee for approval.
Developed in consultation with patients, staff and external mental healthcare providers, the model emphasises evidence based treatments to ensure patients have access to appropriate and effective therapies which provide good value for money.
Flexibility was another big consideration. “The project had taken a long time to progress from concept stage in 2009 to preferred bidder in 2013, and they didn’t want a facility with out-of-date technology – they wanted flexibility and futureproofing built in.
“We agreed to flexibility in the design cut-off dates so we could keep the technology specification open as late as possible, which meant the trust could have the most advanced technology on the market.”
Kier Broadmoor 8923
Kier was appointed preferred bidder in July 2013, and subsequently brought in architect Gilling Dod to take the design to RIBA stage F.
“There wasn’t a huge amount we tinkered with as it was largely driven by clinical requirements,” Mr Giles points out. “The design had to follow the High Secure Building Design Guide – which includes things like clear sight lines and clearly defined areas for patients and non-patients.”
The scope of the project includes the construction of three new ward buildings, named Northern, District and Jubilee after the London Underground lines following a patient vote.
A total of 10 new wards will comprise 162 bedrooms plus associated staff facilities. Overall, this will give the hospital 16 wards and 234 beds, including existing facilities that are being retained.
Also in Kier’s contract is the Central Building, which will house therapy rooms, accommodation for hospital staff and kitchen facilities. Other works include a new entrance building, a single-storey therapy building, hard and soft landscaping, and a new secure perimeter.
“The precast approach has allowed a considerable reduction in the number of operatives on site”
Steve Giles, Kier
Most of Kier’s work is on a 100,000 sq m site in the north-east corner of the Broadmoor estate, which is separated from the live hospital by an interim secure perimeter. The most striking and challenging feature of the site is its slope: it falls away steeply to the east, with a 10 m drop overall.
“This meant a cut-and-fill exercise involving 180,000 cu m of material was required to level areas of the site for the new development,” Mr Giles explains.
The groundworks phase included building around 400 m of retaining walls – cast in situ – across the site to the east of the new ward buildings. Additionally, 250 m of 16 m-deep sheet piling was installed to retain the earth at the front (western side) of the Northern and District wards. “All material has stayed on site for landscaping and fill,” Mr Giles adds.
The foundations are CFA piles with a suspended raft. Kier has used 423 piles of 500 mm diameter and 138 piles of 450 mm diameter, driven to an average 13 m depth.
Spreading the risk
Precast structural frames have been used on four of the buildings – the wards and the entrance – and this has involved more than 6,000 precast components. Such is the scale of the precast element of the project, Kier has used four different suppliers to reduce capacity risk.
“There is a lot of repeatability in the precast components – the buildings were designed with that intention,” Mr Giles says. “Less than 10 per cent of the panels are bespoke.”
The Jubilee ward building is two storeys high, while the Northern and District facilities are three storeys, each one with basements containing M&E plant. The roofs have an unusual turreted design, and use structural steel designed using BIM.
Kier Broadmoor 5202
The ward buildings are cut into the existing topography, so the front (western) elevations appear to be just a single storey, whereas all the storeys on the rear (eastern) elevations are exposed, facing out towards the secure perimeter.
“The precast approach has allowed a considerable reduction in the number of operatives on site,” Mr Giles explains.
“At peak, the four precast buildings required a quarter as many as the Central Building (built in situ), which required 60-70 workers. So by using precast instead of in situ for these four structures, we effectively reduced the number of workers required on site by about 200.”
The precast panels on the ward buildings are large. The biggest, supplied by Techrete, are 10 m high and 4 m wide. “The original design had a rendered facade; we replaced this with these panels, which have pre-finished concrete.”
Security influences design
For the bedrooms, the panels are 4.2 m high and 4 m long. “One of our objectives was to reduce the number of joints, because in the bedrooms the wall finish must be as seamless as possible so patients can’t secrete objects in cracks,” Mr Giles says.
“The original in situ design included 18 joints in each bedroom and we reduced that down to just four. All the MEP channels and other penetrations had to be cast in, which required sign-off by the trust well in advance.”
“Sight lines are a crucial part of the design, so clinical staff were able to view these using the BIM walkthrough. In the entrance building, it was possible to walk through the whole signing-in and search hall experience”
Steve Giles, Kier
The bedrooms are shaped as irregular polygons. “None of the internal clinical areas have right angles, which is a requirement of mental healthcare design,” Mr Giles says.
“All the finishes are as smooth as possible to avoid ligatures [in mental health design, ligatures are considered any projections that could be used for self-harm by patients]. The bathroom wall finishes are trowelled-on resin.”
The three-storey Central Building is the only in situ concrete-frame structure. “The original design was for an infill envelope with wet render, which required a lot of scaffolding,” Mr Giles explains.
“We replaced that with a steel-framing system. This eliminated the need for scaffolding and wet trades – meaning improved safety and quality. Also, as this was right next to the secure perimeter, we removed any concerns about having so many trades working near the live hospital.”
Kier Broadmoor 8937
BIM was used extensively for the design and to plan the construction.
“Every component on the project has its own identification number. During the construction of the precast elements, for example, we used the BIM model to schedule deliveries and allocate hook time. We can trace the whereabouts of any component on the project just by looking at the model.”
BIM was also useful to provide visualisations for the trust. “Sight lines are a crucial part of the design, so clinical staff were able to view these using the BIM walkthrough. In the entrance building, it was possible to walk through the whole signing-in and search hall experience, which helped inform the trust’s operations procedures.”
Mr Giles says the trust wants Kier’s BIM model to be used by the hospital’s facilities team. “The intention is that we will provide O&M documentation from our model, and they will use that as an asset register to manage their operations,” he explains. “They will be able to bring up information on any component, from doors and windows to boiler parts.”
The redevelopment is now well on the way to completion. But before that, there is a rigorous commissioning phase. “The project has to be defect-free, and this means absolutely zero defects,” Mr Giles says. “The word ‘snag’ is banned on site.”
The testing process actually began before the ward construction, when Kier built a full bedroom prototype to check its robustness. “Initially, we built a prototype in timber, to set out the geometry, furniture layouts and sight lines. The clinical staff and patient groups were able to inspect and approve.
“Relative to phase one, phases two to four will take a long time because we will be working within the secure perimeter, so it is classed as escorted works”
Steve Giles, Kier
“Then we did a precast prototype with all the finishes, including sanitaryware and working windows, which were tested using the procedure in the High Secure Building Design Guide.
“The polycarbonate windows in the original design did not stand up to this testing, which is partly why they were replaced. We came up with a new window design, which provides more light and ventilation through a sliding grill feature.”
Kier’s contract is split into four phases, the first of which represents about 90 per cent of the project value and is scheduled to complete in February 2017.
Phases two to four involve demolition of the buildings on the existing Broadmoor site – although some elements such as the Grade I-listed gatehouse are being retained – once patients have been decanted and moved into the new wards. “There will also be a cut-and-fill exercise of about 20,000 cu m, plus landscaping and external car parking,” Mr Giles adds.
These phases, though a small proportion of the overall project value, will not complete until February 2020. “Relative to phase one, the work will take a long time because we will be working within the secure perimeter, so it is classed as escorted works,” Mr Giles explains.
Logistics versus security
Kier’s logistics planning has understandably been shaped by the constraints of the secure Broadmoor environment.
Some of the works have involved small-scale refurbishments inside the live hospital, which require a Broadmoor escort at all times. The main building site is screened off from the hospital by an interim secure fence, though Kier still has restrictions on its operations.
“If we need to work within 8 m of the fence, we have to provide method statements that must be signed off four weeks in advance,” Mr Giles explains. “The same notice is required for use of the tower crane because of concerns about over-sailing.
“For extended working periods – for example, when pouring the floor slabs the power float often goes on into night time – we need to warn ward managers.”
At peak, the site used four 180 tonne-capacity Liebherr crawler cranes and one tower crane, plus three to four mobile cranes in support. “During our busiest period, there were 180 deliveries a week for precast components and another 30 a week for other trades.”
Although the precast design reduced operative numbers, Kier has now reached the labour-intensive fit-out phase, with up to 550 workers on site. “So far we have achieved 900,000 RIDDOR-free hours,” Mr Giles says.