The contractor has navigated Roman ruins and shifted its approach to cope with soaring temperatures as it overhauls a long-neglected part of the city.
Project: Project Medius
Client: Charles Street Buildings Group
Main contractor: Morgan Sindall
Contract value: £48m
Contract type: JCT Design and Build
Start date: March 2018
Completion date: December 2019
Closed under the Beeching cuts in 1969, Leicester’s Great Central railway station and much of the surrounding land has been largely neglected in the decades since.
Now a mixed-use development is set to transform the area, providing much-needed hotel and office space and eventually bringing the station building and its Victorian splendour back into use.
Main contractor Morgan Sindall has taken on the £48m project for developer-client Charles Street Buildings Group, and has already made significant progress towards the scheme’s December 2019 completion date.
“It is part of a move to regenerate Leicester city centre and help link the area around the Great Central station with the rest of the centre,” says Morgan Sindall’s Leicester-born project director Richard Frape.
The development involves the construction of two linked hotels – a Novotel and an Adagio ‘aparthotel’ – alongside a five-storey office and a major highways and traffic management scheme. There are also landscaping and public realm works to be carried out as part of the deal, but client Charles Street Buildings Group will be working on car parking and the redevelopment of the station building itself under a separate contract.
Project Medius Morgan Sindall Charles Street Buildings Group 2
“The client is an experienced contractor and developer,” Mr Frape explains. “It is nice to have [one] that understands the industry so well and the challenges we face.”
The project will provide 4,000 sq m of space in the new five-storey office as well as 252 hotel beds in total – 154 in the 10-storey Novotel block and a further 98 in the smaller Adagio block.
Inheriting the site as brownfield land after the discovery of the remains of a Roman village, the team was forced to rejig its piling design to accommodate the excavated, plotted, logged and backfilled archaeological remains.
“It was always going to be a concrete frame. We felt it offered a better, more simple solution for the acoustic requirements than any other method”
Richard Frape, Morgan Sindall
In all, 272 CFA piles each 600 mm in diameter have been installed to depths of 14 m across the plot for the hotel, with a further 102 at diameters of 450 mm and 600 mm across the office block. The hotel buildings are being constructed using cast in-situ reinforced concrete techniques, with the material having been preferred over precast concrete or steel solutions.
“It was always going to be a concrete frame,” Mr Frape explains. “We felt it offered a better, more simple solution for the acoustic requirements than any other method. Precast concrete is often used in hotel developments, but there are lots of variants in this scheme and precast measures didn’t really offer us anything extra.”
In fact, with the likelihood of units being ordered from Northern Ireland – a stronghold of precast production – the transportation costs and impact on the project programme meant the cast in-situ solution was the frontrunner from the start.
The single core of the 10-storey block features three lifts in total – two personnel and one goods lift – and has been installed using slipform by Northamptonshire-based specialist concrete frame subcontractor MPB, taking just 15 days to complete once the slipform was launched.
“We chose to slip the core because of the impact on the programme it afforded us,” Mr Frape says. “It went up really quickly, which has allowed us to move onto the rest of the frame.”
Alongside the hotel buildings, a steel-framed office block is also emerging.
The five-storey building features a piled foundation and reinforced concrete floor slab with under-croft taxi pull-in areas. It is due to be handed over at the same time as the hotel buildings.
“There is no real benefit to having a staged handover,” Mr Frape says. “It could impact our working practice and so we will complete the two on the same date.”
Composite steel / concrete floor slabs feature throughout the frame, with an angled fifth floor that slopes inward creating some testing connections for the design team and further questions when the facade is fixed later in the contract.
“We did look at value engineering the upper floor to iron out that angle, but it is part of the architect’s design,” Mr Frape adds. “In all honesty we found that the floorspace wasn’t really affected if we had taken out that sloped facade. We decided it really wasn’t worth it.”
With one tower crane feeding the site, the project team is concentrating on advancing the frame of the main Novotel block first before it brings the lower section up to its full height. This lower section has been advanced to second-floor level and is being used as a storage and materials handling podium to feed the advancing main block, currently at fifth-floor level.
Working through the heat of one of the hottest summers on record has made work challenging for the team. New shift patterns were introduced, as were new concrete mix recipes to combat the effects of the high temperatures on both the workforce and on the concrete itself (see box).
Slab thicknesses across the frame stand at 275 mm on the upper floors, with transfer slabs on the first and second floors seeing thicknesses rise to 750 mm.
Neat but challenging solution
In the residential floors above ground-floor level, the team has installed 1,200 x 250 mm ‘fins’ rather than square-sectioned columns to support the slabs. These enable the teams to bring the wall studs through and hide the fins within the walls without affecting the finished floor area.
While it offers a much neater solution, it’s not without its difficulties, according to Mr Frape. “With all the loading, shuttering and back propping needed, they can be much more awkward to install rather than conventional columns. A lot of people don’t like doing them because of that. They do offer a much cleaner solution though.”
Project Medius Morgan Sindall Charles Street Buildings Group overall view from Vaughan Way
Bathroom pods, fabricated offsite by Hull-based manufacturers Kubex and Modular, are being brought onto site and loaded directly onto the frame. The team used two manufacturers to preserve surety of supply.
Once the frame has been completed, it will be clad with a statement Travertine stone cladding system. “We have already bought the stone and stored it in the cladding manufacturers yard. The client wants the building to deliver a legacy for Leicester,” Mr Frape says.
With more than 12 months to go before handover date, the team has plenty of time to hone that legacy as it brings a long-neglected part of the city back to life.
Dealing with the summer heat
The roasting summer of 2018 has entered the history books as one of the hottest on record. But while the fine weather may have initially benefited contractors up and down the country, it did have its disadvantages for the Morgan Sindall team.
With large pours and searing temperatures, there was a danger the concrete would be unable to radiate its heat of hydration, cure too quickly and become cracked and friable. There was also the concern of the effect the rocketing temperatures would have on the concreting gang themselves.
To combat this, the Morgan Sindall team changed the concrete mix design, opting for a recipe that made it workable for longer periods in the heat. It also changed the gang’s shift pattern so that the team avoided working during the hottest part of the day.
“Normally the gangs do all the prep work early in the morning and then the pour itself later,” Mr Frape explains. “We had to change that around to make sure the team worked outside the worst of the heat. Pouring concrete is tough, physical work. The lads were exhausted after they had finished. We would send them home immediately after the pour completed.”
The shift in working patterns and change in mix have had knock-on effects, with the concrete taking longer to hit the strength the design team had worked to. This resulted in leaving the table formwork and falsework in place longer than anticipated, as well as propping the floors below once those forms had been struck. It also meant a consultation with the structural engineers over the loading the team could place on the slabs as work continued.
“We were getting 24 N strengths at 14 days when we had anticipated 40 N,” Mr Frape says. “We had to take a step back and have a look at the calculations. They indicated that we could work with loads of up to 7.5 tonnes on the loading out slab. Fortunately with our factor of safety, we were still only working with a maximum load of six tonnes.”