Full steam ahead: Willmott Dixon’s railway regeneration project

An ambitious regeneration project to celebrate the engineering triumphs of yesteryear has required some clever engineering of its own

Client: Darlington Borough Council
Total cost: £34m
Contract type: NEC (through SCAPE framework)
Main contractor: Willmott Dixon
Architect: SPACE Architects
Groundworks: Wyn Construction
Piling works: Roger Bullivant
Mechanical: Leybourne Urwin
Electrical: KM Electrical Services Ltd
Fit-out: PLB Ltd
Construction start: May 2022
Expected handover: June 2024

Darlington, in north-east England, has for centuries been a town whose ambition outstrips its physical size. In September 1825, the first steam-powered passenger train pulled away from the town’s station, hauling around 400 people crammed into coal wagons. The boiler was lit by directing light from a magnifying glass (matches would not be invented until the following year).

Darlington in the 21st century retains its inventive streak. The borough council is hoping the £34m regeneration of its Rail Heritage Quarter will transform a niche regional attraction into a ‘Darlington Disneyland’, attracting up to 400,000 visitors a year.

Construction workers face different challenges today than those who built the Stockton and Darlington railway, when young boys were paid eightpence a day to drill holes into stone blocks.

The current project is on the right track, though. Since starting on site in May 2022, the team has completed the first phase, which involved creating two engine sheds to house organisations that look after and restore locomotives.

Willmott Dixon has now turned to the scheme’s final and public-facing component – three heritage buildings known as the Goods Shed, the Carriage Works and the Head of Steam Museum. The contractor aims to have the project ready to open by September 2025, in time for the 200th anniversary of that pioneering train journey.

Visitors to the new attraction will enter and exit through the revamped Goods Shed. Named after its original function as a distribution centre, the Grade II*-listed building has also served as a railway engineering shed, fire station, ambulance station, car-repair garage and, most recently, the home of the Darlington Railway Preservation Society. It will live out the next stage of its life as a reception area containing a shop and cafe, fronted by a statement grand staircase with 300mm-thick C35 concrete side walls, heavily reinforced with H16 steel reinforcing bars incorporated with an A393 steel mesh.

“A lot of people in the locomotive world were a bit up in arms because it is the oldest railway-associated building in the world,” says David Starkey, the project’s design manager.

Because of the building’s listed status, much of the new work has to replicate the methods and materials that would have been used when it was originally built in 1833. For example, the glass being put in the windows is hand-rolled by German specialist Schott in line with 19th-century manufacturing techniques, giving it the irregular surface that is recognisable in old church windows.

Timekeeping

The team discovered that the stonework slabs on top of the wall in one of the roof corners had badly disintegrated because of water ingress over the years. Stonemason St Astier took the stonework away to a workshop, where a new section of stone was bonded to it using stainless steel rods and high-strength resin, before being reinstalled on top of the wall. This relatively minor roof repair threatened to derail the timeline – the team had to file a separate listed-building application in order to carry it out, which took eight weeks to get approved.

A four-sided clock tower sits on top of the building, with one clock face taken out to remove the rubble from inside and fill it back in with brickwork. The tower will be finished with a historic lime-based render, which will match the NLG 2.5 lime mortar with yellow sand used for the pointing of the stone walls. New clocks will be put in – the originals went missing in the 1950s and were later found gracing the top of a Morrisons supermarket in a nearby industrial estate.

If there’s a chill in the air, it’ll more likely be because of the ghost (a stationmaster who reportedly died in the Goods Shed) than poor ventilation. Mechanical & electrical specialist Leybourne Urwin is placing a mechanical ventilation with heat recovery unit on top of a toilet block, built on 250x300mm concrete plinths to spread the load while avoiding having to put in new foundations.

The parapet will be clad in a formica product made to resemble Cor-Ten, a steel with additives that forms a protective rust layer over time. The architects wanted the real deal, but the council pushed back, concerned about the film coming off on people’s clothing.

Keeping it real

Another element of the heritage protection is that material from the original building has to be reused as far as possible. Nowhere is this better demonstrated than in the Carriage Works.

Although it’s not as heavily protected as the other two buildings – the Carriage Works is only Grade II-listed and not II* – great attention has been taken to preserve the feel of the 19th-century engine storage facility as it is prepared for new offices and a learning centre.

“You don’t want a brand-new fancy-looking building,” says Starkey. “If there’s any imperfection, it’s history.”

Where new openings have been made, the stones have been sent to St Astier to restore and use again. The stonemasonry company has been able to manufacture new units out of some of the badly decayed stone. “It’s something you learn from being passed down from generation to generation,” Starkey says.

Hollows in the walls are mostly filled with reclaimed bricks from elsewhere in the building. Many of the original bricks were made in the Darlington area, with pure clay hand-pressed into moulds then baked for long periods in an oven.

With minimal work allowed on the walls and floors, the bulk of thermal performance improvements will come through the windows. The original 4mm timber glazing, around 80-100 years old, will be reinforced with bespoke secondary glazing from Selectaglaze.

A second storey for plant required the erection of a steel frame, but the ground was found to be not very well compacted. To support the frame, groundworks contractor Wyn Construction laid 250mm-thick C35 concrete slabs, reinforced with two layers of A193 mesh, on the floor. “You overengineer things if you don’t know what you’re dealing with,” says Starkey.

On track

Refurbishing the Head of Steam Museum, which will become the North Road Station Museum, has presented some unique challenges. First, the building has some unusual tenants. The inside of the under-construction museum is a labyrinth of scaffolding and tarpaulin, protecting vintage locomotives that were too heavy to be hauled out. Second, the museum was built around the original North Road station (hence the new name). Because the train track slopes, so does the building.

At the top of the structure, where timber louvres used to let out the steam, one end is 150mm lower than the other. This meant plans for traditional patent roof glazing had to be thrown out. Instead, the team is individually installing a series of small double-glazed timber windows, each one slightly differently sized.

Glass enthusiasts will not be too disappointed. Four-metre-long Thermospan structural glass walls are being put in at the east and west gable walls of the building, next to roller sectional doors to let trains in and out when needed. The walls will be finished with Forticrete, matching the existing 390x190x90mm architectural blockwork that was installed during a previous refurbishment.

The Head of Steam Museum renovation faces a particularly tight turnaround. The building has to be ready by March for museum fit-out specialist PLB Ltd to install interactive exhibits that bring the story of passenger railway to life.

For now, it looks like the contractors will accomplish something out of reach for most northern rail operators and arrive at their final destination on time.