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Bam King’s Cross scheme sets frame and BREEAM challenges

Both concrete and steel frames will feature on a project that has benefited from a benevolent local authority.

Project: Regent Quarter – Block D and York Way
Client: Istithmar P&O Estates
Contract value: £31m
Region: London
Main contractor: Bam Construct
Architect: RHWL Architects
Structural engineer: Clark Nicholls & Marcell
M&E subcontractor: GDM Partnership
Start date: December 2011
Completion date: November 2013

There was a time when London’s King’s Cross was a byword for the shadier side of life.

Less than 10 years ago it was still a brave man or lost backpacker who ventured into its all-night drinking dens. But since the end of the last decade the area has been enjoying something of a renaissance.

Playing its part in the gentrification has been the Regent Quarter development, which has seen the Georgian and Victorian industrial buildings sandwiched between York Road and Caledonian Road revamped into a clutch of trendy wine bars, coffee houses, modern offices and apartments.

Contractor Bam Construct is having a major role in this regeneration by delivering a scheme that will see Block D of the Regent Quarter converted into offices and apartments.

Different frames for different areas

“There are old listed buildings and light industrial factory units in Block D,” says Bam Construct senior project manager Paul Joyce. “Part of the scheme involves the old stable blocks for the horses that used to pull the Hackney carriages.

“The stables are on two storeys and the horse stairs are still there. There are also new-build apartments, so we have a mixture of everything.”

Indeed, Block D is divided into separate sections, each of which feature different construction methods. The new-build apartments in D1 are constructed using a cast in-situ reinforced concrete frame, while the offices in D2 feature a steel-frame system.

D3, a mixture of small retail units and apartments, features a retained concrete frame, while the office in section D4 is the listed brick structure of the stables. A further section, D5, features the reconstruction of a two-storey brick-built apartment.

Adjoining project helps scheme

Since winning the £22 million contract for the work at Block D, the Bam team has taken on another £9m project, the York Way section, on an adjoining block on the same site.

“It was another separate project for the same client but we managed to persuade them through the open tender process that it made sense for us to do that scheme, too”

Paul Joyce, Bam Construct

The redevelopment of a former dance studio involves breaking through the existing roof slab, tying in a two-storey steel-framed roof extension and forming openings on each floor between the original dance studios and D2, the new steel office building being constructed under the original contract.

“It was another separate project for the same client but we managed to persuade them through the open tender process that it made sense for us to do that scheme, too,” Mr Joyce says.

Demolition and asbestos strip work had been carried out before the Bam team started on site in December 2011 and Mr Joyce managed to persuade client and project manager Istithmar P&O Estates to wrap the muck-shift contract up with the demolition deal.

Contiguous pile frame support

“It also allowed us to install a row of contiguous piles alongside the west elevation of the Peabody Trust houses,” Mr Joyce adds. “There are 17 piles of 450 mm diameters helping support those residential units.”

Those contiguous piles join the 30 400 mm-diameter and 30 450 mm-diameter CFA piles beneath the reinforced concrete frame of the apartment block, along with the 45 400 mm-diameter and 33 450 mm-diameter CFA piles installed by specialist contractor Westpile, which support the steel frame of the office block.

But it was an agreement with local authority Islington Borough Council that was to prove most beneficial to the progress of the project.

Initially, the site team had intended to unload material through a part-possession of one-way Railway Street and reversing construction traffic the wrong way down it.

And although the council was happy with this arrangement, the police thought otherwise. But without any prompting, the council granted a full closure of the road.

“We had an agreement to place welfare facilities alongside the road and we were reversing lorries for the demolition arisings down it,” Mr Joyce explains. “The police were a little anxious about that and having the closure has proven a massive benefit for us. It has saved so much time and effort.”

Increased space means method change

Instead of having to skip loads of concrete into formwork, the extra room has meant the team could use a mobile concrete pump to place the material.

“We suddenly had room for a pump’s outriggers so we changed our method. It has been much quicker, much more efficient,” Mr Joyce says. “We have been able to concrete a third of a slab at any one time. Without the pump we would be looking at much smaller pours.”

Those slabs are 300 mm-thick traditional reinforced concrete in the apartment block, while those in the office are a thin composite steel/lightweight aggregate concrete construction with rebar mesh, adding up to an overall thickness of just 140 mm.

“We have a BREEAM Excellent target on Block D and a Very Good on the Dance Studio section. The lower rating is because we don’t get as much benefit from material reuse”

Paul Joyce, Bam Construct

Like most city schemes, the project is squeezed on a tight site with space at a premium, so two luffing tower cranes at its northern and southern extremes have been used to move material on and offsite.

These include the rainscreen panels and brickwork cladding that will adorn the residential block, and the glazed curtain walling and insulated render system that is being used on the new office section.

In fact, the site team is busy making some minor amendments to accommodate changes made to the offices, which have been let as one to a publishing company.

This includes the two-storey listed stable building, which features the cobbled floor and shallow-stepped horse stairs up to the open-trussed second floor. It is destined to become a library and features the original salt-lick for the horses.

The site’s differing BREEAM ratings

With just a few months left before scheduled completion of Block D at Easter and York Way in November, Mr Joyce is confident of hitting both time and energy efficiency targets.

“We have a BREEAM Excellent target on Block D and a Very Good on the Dance Studio section,” he says. The lower rating is because we don’t get as much benefit from material reuse. We are at that point now where the job really starts to accelerate away.”

And with the office space already taken and most of the apartments sold, the project will prove another shot-in-the-arm to the regeneration of one of London’s most well-known areas.

Underground heating at King’s Cross

With BREEAM Excellent and Very Good targets, the two sections of the Regent Quarter development Bam Construct is working on feature the typical energy efficiency point-scoring systems. Photovoltaic cells will make use of the unshadowed roofs across the scheme, which themselves will feature ‘biodiverse’ pre-seeded material.

Looking for all the world like the planings from a red decorative aggregate driveway, it does apparently provide a better medium for growth and encourages greater biodiversity than standard systems.

There is also an open-loop geothermal installation that uses the constant temperature of the water table to iron out fluctuations in the heating and cooling cycle of the building.

Featuring a 160 mm-diameter borehole driven 70 m below the surface, it helps minimise the extremes in temperature, improving energy efficiency.

“There is an extraction and discharge borehole connected by a duct, which runs north to south across the site through the main plant room. Basically, it is using the aquifer as a heat sink,” Mr Joyce says.

 

Breaking through for a roof extension

On the York Way former dance studio section of the development, the team is installing a new two-storey steel-framed roof extension to provide extra office space for the new tenants.

By breaking out the existing slab and unearthing the original steel beams, the team has been able to weld new connection brackets to the existing structure and then simply bolt the new frame to them.

But breaking out a 1950s brick-clad concrete and steel building has proven difficult. Initially built by Bam Construct’s forebear Higgs & Hill as a book depository, with high floor loading, it features a very tough 500 mm-thick concrete slab with two layers of rolled rod rebar.

Similarly, the walls are just as solid and have been broken out at points throughout the structure to allow flow-through from the existing brick-faced building and into the adjacent new steel-framed office building of Block D.

“It has been difficult, the concrete is very hard indeed – we have had to use floor saws to get through it,” says Mr Joyce.

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