In Liverpool ISG is nearing completion of student housing that is sat between two historic pubs and features one of the most complex steel frames ISG’s project manager has ever seen. Lucy Alderson takes a look.
Client: Ion Developments
Contract value: £39m
Main contractor: ISG
Groundworks subcontractor: Murraywood Construction
Steel frame subcontractor: Billington Structures
M&E subcontractor: A&B Engineering
Start date: November 2016
Completion date: July 2018
It’s hard to think of a better place to build student accommodation than between two pubs.
ISG is realising this undergraduate dream in Liverpool’s Knowledge Quarter, where it is delivering a 10-storey university halls between a pair of Grade II-listed pubs selling relatively cheap pints – as well as £2.99 breakfasts for the inevitable hangovers.
Next door, the contractor is also building a three-storey Premier Inn at the same time – perfect for visiting parents to rest up once their kids have ordered them to leave them alone.
Both of these new builds will sit on top of retail space also being delivered by ISG. However, complex requirements required a meticulous solution to ensure these new shops could support the two buildings above.
Client Ion Developments told ISG it wanted the retail space to be unpartitioned, so companies looking to lease the premises could decide how much they wanted.
Unfortunately, this meant no structural bracing could be involved – just one of the obstacles ISG is carefully overcoming on this project.
Levelling the ground
The contractor was named preferred bidder in 2014, but it would be another two years until shovels hit the ground in November 2016. This was primarily due to heritage issues with some of the older buildings on site that were set to be removed under the plans.
ISG Ion Developments Liverpool student accommodation 1
ISG used this lengthy delay to work with its subcontractors on how to construct the two buildings and retail space. By the time the planning issues were finally resolved, the team was well prepared for work to begin.
“It was a cut-and-balance job, it was tricky”
Shaun Boylan, ISG
But ISG encountered a problem. The development is situated on a steep slope with about a height difference or around one storey between the back and front of the site. It was clear there was a need for reprofiling by lowering the back-end of the job and filling in at the front, which went below ground level.
“It was a cut-and-balance job, it was tricky,” says ISG senior project manager Shaun Boylan. The team could only access the site from the back, which made it challenging to deploy the ramps needed to get the plant – including a mobile crane and a tower crane – safely down 4 m. “To put a safe ramp in, we had to make it 30 m long, but the site is about 80 m,” Mr Boylan says. “The ramp took out 20-30 per cent of the working area.”
Using a gridline system, operatives demolished two existing buildings and set about the job of levelling. The team divided the site by 12 gridlines, 7.5 m apart, to order the works. A stratum that includes 30 m of sandstone negated the need for piling.
The team needed to demolish two existing buildings on site to clear the way for construction. However, carrying this out on such a constricted site was “very difficult”, Mr Boylan admits.
ISG Ion Developments Liverpool student accommodation 32
The two buildings were located at the front of the site beside the busy Lime Street. Although the team demolished as much of the building as they could by hand within the boundries of the site, they needed to close Lime Street in order to finish demolition from the front.
- 1,300 – Overall tonnage of steel
- 33 m – Student accommodation height
- 15 m – Hotel height
- 5.5 tonnes – Heaviest steel section
- 14 – Weeks taken to build steel frame
- 180 – Peak number of operatives on site
This was a far from straightforward move, as Lime Street provides an important route running through the city centre. “This took a lot of planning with the council,” Mr Boylan explains. “We closed Lime Street for a 48-hour period over a weekend and we worked solidly over that time.”
Once demolition was completed, the team moved onto their biggest challenge: tackling the steel frame.
Beefy steel frame
Making sure the retail space could hold the weight of the buildings above was the most technically challenging aspect of the project, Mr Boylan says. “At the point [ISG] went into contract, the client didn’t know who would be letting the retail space and wanted maximum flexibility,” he says. “This was a key design challenge right from the outset.”
“Some of the connections – I’ve never seen anything like it. It’s a heavy frame”
Shaun Boylan, ISG
The two-year preconstruction period for the project was predominantly used to design this complex steel frame. Because the need for maximising retail space had prevented the use of bracing, a complex ‘moment frame’ had to be developed, entailing thick beams every four or five gridlines to “beef up” the structure.
“Taking the bracings out of the retail space and adding the moment frames has added the best part of 300 tonnes,” Mr Boylan says. “Some of the connections – I’ve never seen anything like it. It’s a heavy frame.”
The steel frame’s overall weight is 1,300 tonnes and it took 14 weeks to erect. The mobile crane both constructed the steel frame and brought up materials as the steel frame went up, Mr Boylan explains. “As we built out the frame gridline by gridline, we got to a point where we needed to take the mobile crane out, else it would have been stuck on site.”
The last three gridlines were built using just the tower crane, with each one taking around two weeks.
ISG Ion Developments Liverpool student accommodation Lime Street 3
Another complication has been the need to build what Mr Boylan calls a “floating substation” above the retail space, which will contain all the plant for the building. This meant that a small part of the ceiling of the retail space needed to be boxed out and lowered so that the plant will protrude slightly down into it.
Again, meticulous planning was needed to make sure the frame could cope with this added weight. “One of the subcontractors says he’s now put that he has worked on a floating substation on his CV,” Mr Boylan says. “It was very complex.”
I ask ISG’s project manager if he has enjoyed working on the scheme. “Definitely,” he says. “It’s not often you get to say you’ve worked on what will be a landmark in the city centre.”
Liverpool’s Knowledge Quarter regeneration
Ion Developments’ mixed-use scheme is part of the Knowledge Quarter regeneration taking place within the city.
Under this masterplan, eight sections of Liverpool have been identified for redevelopment and more than £1bn-worth of new developments are now under way.
The Knowledge Quarter Gateway is located between Mount Pleasant, an Old Lewis’ store, Copperas Hill and Lime Street station. This regeneration is predominantly focused on providing new commercial space for tech and digital businesses.
In January, Morgan Sindall won the contract to deliver two phases of work on one of the flagship projects that will be delivered under the Knowledge Quarter Regeneration: the Paddington Village scheme.
Paddington Village is a £1bn project that will provide 1.8m sq ft of science, technology, education and health space. It comprises three phases, with phase one already under way.