Or, how the crack project team put together by developer CIT is setting about the top-to-bottom redevelopment of an entire block of London's West End – and is bringing it in for 83% of the benchmark cost.
"This project is not a simple refurbishment; it is a major redevelopment," says George Kyriacou, commercial director at developer CIT. He is referring to the down-at-heel 1970s office building that occupies most of a block in London's West End that CIT bought in August 2001. The challenge was to maximise the return on investment by transforming the building into grade A modern offices with more lettable floor space and to add a storey of penthouse apartments.
CIT decided to reconfigure the office layout and extend the floors into the building's enormous lightwell. This would involve scrapping one of the reinforced concrete access cores and rebuilding it in a more efficient form and location. The other cores would be modified. With the extended office floors, the lightwell would be about 30% of its original size.
CIT let the contract as a two-stage tender with a guaranteed maximum price, to develop the design with the construction company and ensure it was built within cost. The company opted to use the same construction team for this project as it had on its previous two, and is planning to use on its next scheme.
The challenge for the design and construction team was to carry out the works while keeping the retail units on the ground floor open. And, just to add a little extra spice, the local planners insisted that the developer increase the amount of residential space in the building.
The construction team knew it was not going to be an easy project. One area of particular concern was the need to keep the seven shops that occupy the building’s ground floor open throughout the contract – so the electrical supply and the fire alarm system would have to be maintained. It was a task made all the more sensitive by Steinway Pianos’ occupation of one of the retail units. “They might have visitors like Elton John and Billy Joel come in to buy a hundred-grand piano at any time,” says Kyriacou. The unit is Steinway’s UK headquarters and includes practice rooms for concert pianists as well as a large room, Steinway Hall, where the precious instruments are lined up beneath walls covered with photographs of some of the world’s most famous pianists. Needless to say, construction noise would not be well received.
Demolition commenced with a “soft strip”, in which non-structural elements were removed from the building. Demolition proper started on the fifth floor with the destruction of the reinforced concrete access core near the south wall. This had to be removed to allow the floor plates to be reconfigured more efficiently. Demolition waste was dumped down the stairwell and removed through a hole in the wall at the foot of the core. Next, the top two floors of the west core and the facades surrounding the lightwell were removed to allow the lift shaft to be extended skyward to serve the new residential floor. “The demolition noise was horrendous,” says Kyriacou. A section 61 agreement with Westminster council meant noisy working was confined to two-hour slots because of local residents. It also meant work had to be halted when Steinway had an important client.
A crane was needed to lift plant and materials into, and out of, the central lightwell. There was nowhere suitable to locate a crane at the foot of the lightwell, so a temporary frame had to be constructed on the fifth floor and the structure had to be strengthened to support its weight. The tower crane prevented the contractor installing a temporary roof over the site. Instead, the existing roof was retained for as long as was possible to prevent rainwater entering Steinway’s shop on the ground floor.
The site’s location next to the shopper’s Mecca of Oxford Street meant that hoardings had to be erected around the site to keep pedestrians out. The proximity to Oxford Street also meant that there were onerous restrictions on where and when deliveries could take place. Main contractor Interior negotiated the use of four parking bays adjacent to the Welbeck Street facade to off-load deliveries. “It cost us an extraordinarily large amount of money,” says Bob Hill, Interior’s project manager. The contractor also negotiated the use of a bay beneath the Wigmore Street facade for the removal of waste materials. However, because traffic builds up through the day, Westminster council stipulated that the bay could only be used up to 11am each day. An electricity substation was also installed in the basement to ensure power supply to the retail units.
March 2002As demolition of the core was under way, work began in the basement. Nine piles, each 350 mm in diameter, were installed. These would carry the load from the extended office floorplates and support a goods lift. Interior, the main contractor, had to scour the country to find a piling rig small enough to be manoeuvred along a 1.4 m-wide corridor in the building’s basement and yet robust enough to sink a 350 mm-wide auger pile into the ground. A high water table meant that when the team broke out the existing pile cap to install piles for the lift water flooded into the new excavations. “We had to pump 24 hours a day until the slab was put in place,” explains Interior’s Hill.
With demolition almost complete, the next challenge was to extend the office floorplates out into the lightwell. This would increase lettable floor area from 5200 m2
to more than 6800 m2
. However, before the floor extensions could be constructed, two enormous transfer beams had to be slotted into the heart of the building. Without these, the columns that supported these floor extensions would pass down straight through the Steinway shop. With the transfer beams in place on the first floor, the loads will now be conveyed over the roof of the shop, to the basement piles. The transfer beams were so heavy that the tower crane was not capable of moving them. Instead, a 300-tonne crane had to be brought in over a weekend to lift the beams over the roof and into the lightwell.
Mid-summer and the new structure was starting to appear. The first element was the reinforced concrete office core complete with stairs and two lift shafts. Next, steel frame and steel decking were installed to extend the office floors out into the lightwell, before being carpeted with a lightweight concrete slab.
Once the structure to extend the floorplates had reached second-floor level, installation of the building services began. The services installers, along with the blockwork partitioning gang, chased the steel erectors up the building. Meanwhile, down in the basement, installation of the air-handling units and boilers got under way.
After the wettest December since 1940, work began on the building’s roof. “Westminster’s planning officers required us to increase the number of residential units,” says Kyriacou. To comply, another floor of apartments was to be added on top of the 13 already there to increase the residential units to 23. However, before installation of the new structure could begin, the deteriorated lead mansard roof protecting the existing apartments had to be replaced. “We had to re-lead the whole roof; it cost us a bloody fortune,” says Kyriacou. Interior had to incorporate the £500,000 roof replacement into the programme without affecting the handover date. The new sixth floor was constructed using a structural steel frame a timber-joist flat roof to ensure the foundations did not have to take any additional loading.
Completion July 2003
With work on the roof now storming ahead, the emphasis has switched to finishing the office floors. Inside, work on drylining the perimeter walls of offices is well under way prior to a finishing skim of plaster being added. Outside, hidden beneath the site hoarding, work is progressing on enhancing the facades by replacing windows, installing curtain-walled window bays and cleaning the brickwork. The image above is a representation of what the finished scheme will look like. Despite the weather, Hill is sure the project will meet its July completion date. And Kyriacou is pleased with the scheme, and says the building’s cost at £100 a square foot to category A standard is significantly below cost consultant EC Harris’ benchmark of £120 a square foot for this type of project.