All change: The Stockport Interchange

Jul 17, 2023

A £90m regeneration project near Stockport’s rail station aims to bring new life to the town centre

Lead clients: Transport for Greater Manchester, for Greater Manchester Combined Authority Additional stakeholders: CityRise and Stockport Metropolitan Borough Council Main contractor: Willmott Dixon Customer lead consultant: WSP, working with BDP Contractor architects: Leach Rhodes Walker (residential) and The Harris Partnership (interchange) Contract type: NEC Option A Project cost: c.£90m Construction start: Summer 2022 Construction completion: Spring 2024

Artist LS Lowry featured the neighbouring viaduct in his work. CREDIT: The Crispin Eurich Photographic Archive

A series of photographs from 1962 show the artist LS Lowry looking typically curmudgeonly as he eyes Stockport Viaduct, once the largest viaduct in the world. “I only deal with poverty,” he once declared. “Always with gloom. You’ll never see a joyous picture of mine.” The artist spent his life creating composites of industrial landscapes in his beloved Lancashire. He spent a lot of time in Stockport, and the town’s railway viaduct, which opened in 1842, with its 28 arches and 11 million bricks, features in a number of his works.

While the viaduct remains, the neighbouring town centre site, where Lowry stood in those photographs, now hosts Willmott Dixon’s emerging circa-£90m Stockport Interchange. The town centre location has been cleared a couple of times since the 60s; most recently, an old bus station – a sprawling quasi-car park with various lanes and single-storey shelters – has been put out of its misery.

Now it’s set to be replaced by a modern terminal with 18 bus stands, a covered passenger concourse and shops. The bus station, which will accommodate up to 168 departures per hour, will be topped by a two-acre park linking to the much smaller viaduct structure, Wellington Bridge. The project also includes a 15-storey block of 196 build-to-rent flats, as well as a new cycle path and a 90-tonne bridge to join the interchange to the town’s railway station, situated about 150 metres to the south. The project is expected to be completed in spring 2024.

While it would be unfair to characterise 21st-century Stockport as gloomy, local politicians talk up the scheme’s regeneration potential. The former Labour councillor and leader of Stockport Council Elise Wilson says it will “completely transform the look, feel and presence of Stockport”, adding that “for the first time, we’ll have a fantastic town centre park to sit down and enjoy the amazing views of our impressive viaduct”.

Willmott Dixon has been involved since 2019. The family-run contractor has an approximate £90m lump-sum contract, having been selected through the Pagabo Major Works £50m+ framework. The client for the scheme is Transport for Greater Manchester, a subsidiary of the Greater Manchester Combined Authority. However, it raised funds from other stakeholders, including Homes England, Stockport Metropolitan Borough Council (which will own and run the park), and CityRise, a joint venture between developer City Heart and Rise Homes (which will own and let the housing).

“You can’t imagine the potential implications of doing a development of this nature in the middle of the town and [trying to] keep everyone on board”

Work started on site in summer 2021 after late design changes. “[The client] did some initial designs but they only had one stair core [in the block of flats], and we told them they needed two,” explains Andy Howarth, Willmott Dixon’s operations manager in charge of the project. “The fire officer came along and agreed with us.”

When the order eventually came through, Willmott Dixon began removing the existing bus shelters and foundations with subcontractor Howard Stott Demolition. After groundwork remediation, the team inserted 600mm continuous flight auger piles, which were swiftly drilled 10 metres into the sandstone rock. The project features about 585 piles with 235 underneath the block of flats and 350 beneath the interchange.

What followed was a lot of concrete: in total, the project uses 19,000 cubic metres of it in the scheme’s foundations, the structure of the interchange and the residential tower.

The team started the structural work by building an 8-metre boundary wall to divide the residential scheme from the interchange and park, as some of the interchange’s hefty concrete columns had to be built later or they would be in the way of the frame needed to create the wall. The concrete-frame subcontractor, Mayo Civil Engineering, is Willmott Dixon’s largest supplier for the project, carrying out about £20m worth of work under an umbrella contract covering the interchange and residential building. (Willmott Dixon often splits up parts of the project in its contracts or procurement; here using Mayo MEP and A&B Engineering to do the MEP for the residential and interchange aspects respectively, and RED Systems and Hadrian Group respectively to provide curtain walling for each.)

The residential-build frame is a standard residential frame, says Howarth. The two cores were slip-poured, with the 14-home floorplates later created with in-situ concrete frames, reaching a rate of one floor every six days. Despite the pour only completing in late May, fit-out is well underway, thanks to the use of a five-storey steel-structured protective screen. The screen, which was lifted hydraulically or via crane, keeps out bad weather while windows are added to completed storeys – making them ready to fit out – while floors are poured into place. The residential building is being clad with brick slips over rock-wool insulation, while the windows feature aluminium frames.

The interchange structure is more complex. It is held up by 7-metre-tall circular concrete beams – 73 in total – onto which the builders poured 109 beams up to 2.2 metres deep and 15 metres long before laying a slab. The western edge of the slab is cantilevered as it meets Wellington Road, where people will be able to access the new park, as no load is permitted on the Grade II-listed Wellington Bridge structure. “That was some specialist, unusual stuff,” says Howarth. He adds that “making sure that the thermal movement is accounted for” through movement joints over such a large structure was one of the toughest technical challenges. This was especially true given the need to ensure they did not affect the placement or hanging of the cladding – which could not be cut on site.

Now that the pouring is done, Willmott Dixon has begun work on the park, which will sit above 1.2 to 3 metres of build-up on the slab. The build-up is lightweight, reducing the amount of concrete required in the structure: most of it will be made of polystyrene void former, while plants will sit in a specialist ultra-light GeoCell rock substrate.

The build-up also features an innovative drainage system to help tackle flash flooding. The slab is topped with a waterproof polyurethane layer, on top of which sit 85mm blue roof attenuation cells. When it rains, water will pass through the porous park surface and sit in the water cells until it is discharged into the Mersey once the river has calmed.

At the edge of the park, a large oval hole in the slab, dubbed the Oculus, reveals the ground-level circulatory area for buses. The terminal features glass curtain walling on the interior facade of the Oculus and on its external walls. The original designs had the rectangular slabs hung horizontally, but Willmott Dixon realised this would be tricky on a curved building so, after some design development, opted to install the cladding vertically.

Despite the technical challenges presented by the complex scheme, which has had up to 300 workers on site at once, the contractor’s hardest task has been keeping everyone happy. This is partly down to the abundance of clients and stakeholder bodies, let alone various planning, highways and arboriculture teams at Stockport council.

“Their requirements aren’t necessarily what you might think,” says Mike Lane, Willmott Dixon’s director of operations for the North of England. “They’ve got a really different view on anything from the layout, [to] the type of product [we use and] the sort of people that might use something – and often we have to give that a fair bit of consideration.”

A bigger challenge is keeping locals happy while occupying a large and highly visible part of their town centre over several years. “You can’t imagine the potential implications of doing a development of this nature in the middle of the town and [trying to] keep everyone on board,” says Lane.

Nevertheless, Willmott Dixon has worked hard to win over residents and businesses. It has created 57 local jobs, provided 97 weeks of apprenticeship training and 11 weeks of work-experience, as well as teaching local schoolchildren about construction – and, when Construction News visited, a group of special-needs children were departing the site office after enjoying a virtual reality session. It has also directed 56 per cent of its project spending towards firms within 20 miles of Stockport.

All in all, the contractor reckons it is helping to create new life around the old Stockport Viaduct arches. “It’s not to say there aren’t people who have come up with challenges and put them at our door,” says Lane, “but the mood music is really quite positive and people see this level of investment on their doorstep, and it has landed pretty well.”

Willmott Dixon has installed a 90-tonne Cor-Ten bridge as part of the Stockport Interchange project. The 40-metre bridge stretches from the podium of the residential building, which sits at the same level as the new park, to a raised bank, where the firm is inserting a cycle path to Stockport station. The bridge, which is 5 metres wide, arrived on site in two parts before being welded together. It was then picked up on a mobile platform and moved into place before – on a Friday night – being craned onto two concrete abutments by a 750-tonne crane. The cycle path to the south of the site is still under construction; Willmott Dixon has inserted sheet piles into the steep banks to shore up the ground before building the path.