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At first sight, the three towers under construction in a quarter-mile stretch of London鈥檚 Bishopsgate near Liverpool Street station are nothing out of the ordinary. The area has enjoyed a long, uninterrupted construction boom as these sites form part of the Eastern Cluster, the area of the city designated for tall buildings.

Two of the towers, 22 and 100 Bishopsgate, conform to the bog-standard, all-glass, worker-in-suits typology, but the third is for people in dressing gowns. Now marketed as One Bishopsgate Plaza, 150 Bishopsgate packs a 237-bed five-star hotel in the lower half of a 43-storey tower with 160 apartments above. At a stroke, this quadruples the number of residents in the Eastern Cluster 鈥� a City of London survey in 2018 revealed that the area housed just 49 apartments.

Two other features differentiate the 拢300尘 project from its high-rise neighbours. As the name One Bishopsgate Plaza suggests, the development features a public square in front of the tower, complete with a glazed pavilion for entry to a triple-height, 400-seat, below-ground ballroom. The north side is bordered by a five-storey listed terrace called Devonshire House, which will house restaurants, retail and offices. This scheme is being developed by Stanhope on behalf of Singaporean property company UOL and is being built by Lendlease.

Complexity is added to this multipurpose scheme by a full fit-out, a role that is new to Stanhope. This involves co-ordinating four fit-out specialists 鈥� one for the apartments, another for the hotel bedrooms, a third for the hotel front of house plus another for the back-of-house areas. The tenant fit-out of the spaces in Devonshire House also needed to be factored in. A careful approach to procurement and construction was needed to ensure that UOL鈥檚 first UK project fully met expectations.

Lendlease project director Paul Sims jumped at the opportunity to lead this job for the firm, giving up his role as the firm鈥檚 head of operations to take it on. He describes the decision as a 鈥渘o-brainer鈥�, rattling off a list of 鈥減henomenal challenges鈥� that tempted him to make the switch.

Bishopsgate is host to a stream of people, buses, taxis and cars

These include a four-storey basement, a third-floor swimming pool and cantilevered slabs on the tower to maximise views over the city. The site is constrained by the Metropolitan tube line, which runs 1m below Devonshire House, and a four-storey electrical substation hems in the site at the back, with Bishopsgate at the front. 

Just 150m from Liverpool Street station, Bishopsgate is host to a stream of people, buses, taxis and cars. 鈥淚f you get into construction and want to tick off all the things that say you have lived your life in construction, it鈥檚 all in this project,鈥� Sims says.

UOL owns the Pan Pacific hotel brand and snapped up the site when it came up for sale in 2014, as the previous owner had planning for a Four Seasons hotel. Keen to avoid taking on construction risk in a new market, UOL put the job out to competitive tender.

Bouygues and Mace were bidding for the scheme when UOL brought in Stanhope as development manager. It advised UOL to step back and review the procurement strategy.

Flexibility to innovate

UOL needed plenty of time to ensure the hotel interiors matched its aspirations for what will be Europe鈥檚 first Pan Pacific hotel. Stanhope advised that this would throw the programme off track as the interior design had to be finalised before contractors could bid for the work.

鈥淭here could be nine to 10 months of procurement before getting on-site,鈥� says Gary Taylor, Stanhope鈥檚 Bishopsgate Plaza project director.

Stanhope recommended UOL switch to construction management to enable procurement on the early-work packages to start immediately, while UOL continued honing the interior design.

Complex gridshell roof over Devonshire House was simplified to make it easier to build

鈥淎t Stanhope we always want to get our projects on site as soon as possible and construction management gives us the flexibility to do that,鈥� Taylor says. 鈥淚t also gives us the flexibility to bring in trade contractors who can help with innovative solutions to problems. If it was a fixed-price contract, you would hand all that control over to the contractor.鈥�

The switch to construction management also gave Stanhope time to review other elements of the job that risked adding cost and time to the programme. The structure and services were simplified, bathroom pods were introduced for the hotel and apartments to bring greater certainty to the programme and the complex gridshell roof over Devonshire House was simplified to make it easier to build.

The apartment layouts were tweaked and back-of-house space in Devonshire House moved into the tower to get more value from the site.

Keltbray was engaged to start work on the basement. The area around the core was built using top-down construction to provide a working platform to get ahead on the core, with the rest of the basement excavated conventionally.

Progress on the core work was given a further impetus by Stanhope鈥檚 decision to switch from conventional in-situ concrete to twin wall concrete panels at level B1. The contract for the building鈥檚 concrete frame and post tensioned slabs was awarded to Expanded.

鈥淲e got seven months of construction progress and a start on the frame, which would have been impossible with a traditional contract,鈥� Sims says.

Meanwhile, UOL was using this time to hone the interior design of the hotel. A space on the third floor was earmarked for a bar, but UOL wanted to evaluate whether this area would provide a better return as meeting rooms that could be rented out by the hour.

The complex fit-out was one of the biggest risks to the programme

The change of procurement route had bought it three months to decide without affecting the programme. It opted for meeting rooms. This flexible approach also allowed UOL to choose what lifts it wanted while the concrete was being poured in the basement.

Specialist contractors were brought in early to suggest ways of saving time, with the promise of winning the packages they were advising on.

The complex fit-out was one of the biggest risks to the programme, exacerbated by the fact Stanhope was working with unknown specialists as it had not done a full fit-out before. Fully fitted out bathroom pods helped, but the fully panelled hotel bedrooms were complex to deliver.

鈥淗ow do you do that in an efficient way given there is a huge number of men and amount of movement on the site with the consequent risk of damage?鈥� Taylor asks.

A firm called B&B Italia was brought in to handle the hotel bedrooms and suggested a prefabricated panel system that quickly clips onto a frame. 鈥淚t鈥檚 a Swiss watch in terms of design,鈥� Taylor says. 鈥淭his would have been very labour intensive if done traditionally.鈥�

We think it is the largest riser in the UK

David Tooley, Lendlease

A similar approach has been adopted in the apartments, with prefabricated bathroom pods and utility cupboards containing the ventilation and heat interface units for cooling and heating. The main service riser is prefabricated and extends over 47 floors.

鈥淲e think it is the largest one in the UK,鈥� says David Tooley, Lendlease鈥檚 head of building services. A point cloud survey of the riser shaft was done to understand how this varied dimensionally along its length, he says.

Lowered down the shaft

Armed with this information, a tolerance of 20mm between the shaft and riser frame was determined. Each riser section includes the structural frame and services and varies between two to three floors tall depending on weight and was carefully manoeuvred down the shaft by tower crane.

The most delicate structural elements were the tower bays. The north-west and south-eastern corners of the tower feature an all-glass, v-shaped projecting bay extending the full height of the building to maximise views over London.

The architect PLP wanted to avoid heavy columns obscuring the views, so the bays are suspended from slender steel rods extending diagonally from the main frame to the edge of every forth slab. Intermediate slabs below are supported with vertical rods attached to ends of the diagonal rods.

This structure, including the compression members that restrain the lateral forces generated by locks on the diagonal elements, is clearly expressed on the building exterior. During construction, the loads had to be transferred from the temporary supports used to build the bays to the rods with the glass in place. 鈥淲e had to make sure we released the loads extremely carefully to ensure the windows didn鈥檛 crack,鈥� Sims explains. 鈥淲e鈥檝e done it without breaking a single pane of glass.鈥�

Managing men and materials

The complex services and fit-out in the tower called for careful management of men and materials. Space is extremely limited on site and deliveries are made outside working hours. These are brought to site and distributed to the floor where needed and waste is taken away at night. This keeps hoists free for workers during the day.

Materials must be used quickly to avoid the site becoming congested. 鈥淚f anything is on the floor for 48 hours, something has gone wrong,鈥� Sims says.

A software tool called Sablono is being used to streamline the handover between specialists working on the hotel bedrooms and apartments. Each floor has a QR code pinned to the wall, with another QR code used for each apartment or hotel guest room.

By scanning the code, workers armed with iPads can bring up the schedule and drawings for the area. The tool contains all the details of what needs to be done and who is responsible for doing it 鈥� and workers can log the progress made each day, including photographs. This means follow-on trades can be confident that tasks have been completed and everyone with access to the tool can keep remote tabs on progress.

鈥淚t saves those huge piles of paper back in the site office and means you can hand over from trade to trade instantly,鈥� Tooley says. Sims adds that the tool has helped improve relations between the trades.

The basement will have storage for 350 bikes along with changing rooms

Sims says the 120-year-old Devonshire House was in poor condition. 鈥淲e had to do an awful lot to make the structure safe,鈥� he says. The front structure had to be renewed and stitched into the existing elements. The south facade also had to be renewed, with the west and north sides restored.

The basement will have storage for 350 bikes along with changing rooms. The project will enter its most intense phase when tenant fit-out starts on Devonshire House over the next three months. When the project is completed towards the end of this year, the plaza will become a welcome outdoor destination for office workers with the tower busting the all-office dynamic of this part of the city for good.