Hybrid welfare: MTX mixes modern and traditional

A blend of building methods is speeding up the construction of a new centre at Colchester Hospital. Colin Marrs reports

Project client: East Suffolk and North Essex NHS Foundation Trust Total cost: £50m Contract type: JCT (two stage via NHS SBS Framework) Main contractor: MTX ContractsArchitect: IBI Structural engineer: Rossi Long Groundworks: RMB and Flori Construction MEP: Halsion Drylining and ceilings: SCL Interiors Construction start: October 2022 Expected handover: April 2024

The north-Essex town of Colchester is growing fast. The former Roman settlement already boasts a population of 197,200, the largest of any non-unitary district council in England. By 2031, that headcount is expected to rise another 14 per cent to 225,000, a rate of growth among the fastest in the country. But such quick expansion comes with pressures – not least on the public services needed to support health and wellbeing.

Waiting times for joint replacement procedures – particularly for hips and knees – were among the worst in the country in 2018, which was when the Colchester and Ipswich hospital trusts merged to form East Suffolk and North Essex NHS Foundation Trust.

“We faced a 14-week delay and it’s all been mitigated through resequencing the scheme. I don’t believe in a traditional build you could mitigate that sort of delay”

Five years later, the trust is creating one of the largest elective orthopaedic centres in Europe, being built by modular contractor MTX Contracts on a quarter-hectare plot on the edge of Colchester Hospital. The centre will be named after the late orthopaedic surgeon Dame Clare Marx, the first female president of the Royal College of Surgeons of England, who worked at the hospital for 27 years.

MTX is using what it calls a “hybrid” approach on the job, combining the best of modern methods of construction (MMC) and traditional building techniques. When the job finishes in April next year, the firm will hand over a 10,800 square-metre facility providing eight operating theatres and 72 inpatient beds over three storeys. The trust says the added capacity will allow it to double the number of orthopaedic operations it performs from 5,000 to 10,000 and help to slash waiting times back to the 18-week standard.

The MTX team arrived on site armed with a plan. Modules would be shipped in and lifted by crane onto an L-shaped 300mm-deep power-floated poured concrete slab.

However, as is often the case in construction, things didn’t quite go to plan. The sloping site along with height restrictions imposed at the planning stage meant a basement had to be created to level the ground floor and house services. During this process and subsequent piling operation, contaminants and large rocks were discovered by groundworks subcontractors RMB and Flori Construction, slowing down work and posing a threat to the schedule.

With a traditional build, this sort of delay could have been disastrous. However, the project team took advantage of the flexibility allowed by modular construction. They changed the schedule and the plan to instead create the ground-floor slab in sections. This meant construction could start on those areas of the site where the basement was not required – around 2,950 square metres – and this allowed the first batch of modules to be craned on and fitted out. Meanwhile, groundworks continued on the rest of the site to construct the basement and the 550 square-metre slab it supported, and complete the base for the new building.

Overall, 12 concrete columns measuring 400mm x 400mm x 2,600mm were cast into the slab. Together with four reinforced concrete walls, these columns hold up the basement ceiling – a 300mm reinforced slab formed on tables as a seamless continuation of the ground floor

“We faced a 14-week delay and it’s all been mitigated through resequencing the scheme,” says Scott McCaskie, a director at MTX. “I don’t believe in a traditional build you could mitigate that sort of delay. The trust’s structural engineers were amazed that we could still maintain the programme.” Eventually, the ground issues were solved; flight auger piles between 6 and 18 metres deep were driven in and the basement was completed. It will host plant including wet services and water tanks.

Almost 300 modules used in the construction – engineered open structural steel frames – were craned to the site in three phases, with fit-out work continuing between each lift. The modules are a variety of sizes and weights – the lightest being 7.2 tonnes and the heaviest around 11.5 tonnes. The standard units for open areas were made by manufacturer Lewis, and came with a fire board and a metal deck fitted to the floor. Other units came with floors with openings for risers, and even staircase units, while external and roof units were fitted with a waterproof membrane on the roof.

The Lewis decks are formed from steel shaped to create a regular dovetailed trough at intervals across each sheet. These sheets acted as reinforcement for a 90mm concrete screed across multiple modules to create seamless floorplates. MTX says this approach is now standard across many of its buildings.

Walking around, the effect is tangible. The floor feels as solid as any in a building using thicker, fully poured concrete slabs. “These are a world away from traditional prefabricated floors,” says Dan Harrad, senior project lead at MTX. “We’ve done tests on a similar build we did in Oxford [at a critical care building at John Radcliffe Hospital] and it performs as well as, if not better than, the building next door that was built traditionally.”

Internal walls are being built with full boards made from rockwool insulation sandwiched between oriented strand board and plasterboard. They are held in place by deflection heads manufactured offsite, which allow for slight movement in floors. However, some board-cutting takes place onsite for intricate areas around windows and doorways. Glassroc board is formed and sealed to box-in the columns.

The team is aware of the fire risk from cavities in modular buildings but says that these dangers have been engineered out. “It’s about managing the materials and sealing properly to minimise the risk of fire getting in in the first place,” says McCaskie. “Our fire consultant is also authorising engineer for the trust – working across both parties gives extra assurance.”

The size of the scheme increased midway through the planning process – adding two more operating theatres after the trust received extra government money following Covid. This has led to the creation of a separate plant area on a roof to serve the new theatres. Two large chillers will sit on top of anti-vibration pads attached to glass reinforced plastic open-mesh grating – made from recycled materials – on the 115 square metre chiller deck. “The grating spreads the load and ensures the chillers are on an even surface, as the roof slopes slightly for drainage,” says Harrad.

The external walls on the ground floor and above will see glazed curtain walling combined with rainscreen cladding, fitted on top of weatherboard and a vapour barrier. Where the basement walls show above ground, the envelope will consist of brick slip contained in gabion baskets.

Unsurprisingly for a building procured through the MMC-focused NHS Shared Business Services framework, there is very little blockwork, with the exception of lift shafts built floor-by-floor as more units are added. “We’ve got four to six weeks between lifts so there is no benefit on this project of using prefabricated methods,” says Harrad. “Doing it this way means that we don’t have to build round the shaft.”

MTX has been in the modular sector for more than two decades now. The Colchester facility, with its poured concrete floors, shows that construction needs to avoid falling into the trap of seeing traditional versus MMC methods as binary.

“In our early days we used to think that we had to push for everything to be done offsite,” McCaskie adds. “Our ethos is to continually review and improve our processes to work out whether there are areas where we can achieve extra efficiency but still provide assurance around the quality. We believe the hybrid approach we have taken here provides the best reassurance.”

MTX delivered the new building via a two-stage contract. It won the preconstruction services contract in 2020 and worked with the trust to bring the design to RIBA stage four. “I think that schemes with two stages mean you are working more collaboratively as a team, because of the way you go through the journey together to get to that stage four,” says Scott McCaskie, a director at MTX. “We’re basically doing it open-book and taking the client through the journey by testing the market and fixing the price. I think it helps the client get a better-quality project.”

The project was granted planning permission in June 2021. After another tender process, MTX was appointed as main contractor in April the next year. However, this was slap bang in the middle of the hyper-inflationary period sparked by the Ukraine war. Nervousness over rising materials costs and an agreement that the trust would not go back to the government for more money meant it would be another six months of negotiation before the final contract was signed.

Ultimately, a clear nine-point agreement was agreed on that shared the inflationary risks. In the end, materials prices have since stabilised, meaning that agreement has not been stress-tested.