Client: RIU Hotels & Resorts
Location: Victoria, London
Completion Date: 2023
Main Constractor: McLaren
M&E Engineer: HESIMM/Forman Roberts
Other Team Members: Colorminium
The original building, designed by Ove Arup in the 1960s, was one of the first to feature the use of post-tensioned concrete outside of bridge structures. Designed initially as offices featuring a basement car park and retail storage, the building later included a flagship Woolworths store at ground floor level. The structure is broken up at ground floor with the two wings of the building rising before re-joining at the second floor with a 20m post-tensioned box girder transfer structure over the roadway beneath.
The building underwent major renovations during the 1990s by Buro Happold, who removed some of the internal concrete shear walls and replaced the main façade on the tower. A new entrance was introduced from Wilton Road in lieu of the previous access point from Vauxhall Bridge Road and a glass rotund was added as the new feature entrance. As part of the works, the former inset concrete roof was demolished to make way for a new plant room and for open office space in steel construction, removing the internal columns. Extension pods were added cantilevering from the bookcase shear walls at each end of the building to provide MEP services to each of the office floors, thereby minimising ducting and maintaining good headroom.
Now, 30 years later, the building has undergone another large-scale refurbishment by Evolve to further utilise the space on site. Extension structures are proposed to the three low-level podiums of varying heights between one and three additional storeys. External plant gantries are added to the rear of the structure and to the rooftop, in order to service the new bedrooms. New extensions to the tower floor plates and a lightweight lift shaft are threaded into the structure to provide enhanced passenger movement around the building.
As part of the works, the project includes the removal of transfer structures and infilling of former works as well as a full replacement of the building façade, including removal of the former moment frame edge beams across the podiums.
Evolve worked closely with the architects and MEP consultants to ensure that the structural integrity of the building wasn’t compromised as a result of the change of use and proposed works. Due to loading constraints, and without the option to strengthen the existing foundations, a series of load balancing exercises were carried out to compare the loads induced on the building under its former refurbishment and original construction. A series of lightweight construction methodologies were subsequently adopted. The structure was formed with a Lytag concrete and composite steel structure on hotel floors, and lightweight profiled metal deck roofs. Architecturally, the floor build-ups were created using an acoustic timber batten raised flooring system and plant was carefully located to utilise the spare capacity in the building. Combined, these actions helped to minimise the change in load induced on the pad/piled foundations to within 10% of their original 1960s design load.
Although the façade of the main tower was replaced in the 1990s, the low-rise podiums to the building still featured the original 1960s façade and concrete upstand beams around their perimeters. In order to accommodate the new storey-deep windows, these beams would need to be removed. The beams formed part of the overall stability of the podiums through frame action and supported the cantilever corners of each podium. A new series of steel beams and portalised frames were inserted into the façade, allowing these elements to be removed and significantly opening up the elevation, which enabled the new façade to be upgraded to modern thermal and construction standards.
Each of the tower floor plates were extended out with new lightweight concrete cantilevers springing from each of the column points. A wrap-around bracket system on the columns was devised to create a compact structural arrangement, and to minimise the impact to the architectural finishes and loss of space locally to the columns.
At second floor level, a change of column grid in the original building was required, switching from the relatively closely spaced column centres of the office floors to a larger spacing more suitable for the retail units below. These transfer structures were formed in a 3m deep concrete beam in which bedrooms were proposed to be situated. Consequently, a new load path for these columns was required, taking the load of the formerly transferred columns down to basement level and installing new transfer beams within the ground to bring the loads back to the original foundation points.
Due to the structure being split by the road at the lower floors, lift access to the north wing was very limited. Consequently, a new lift shaft has been installed, carefully threaded through the building. The pit of this shaft is in the former retaining structure of the basement walls; as a result, the area was underpinned to create the new lift shaft and to maintain the continued support of the building above. A lightweight custom-built steel frame has then been inserted between the former pod structures, bolted onto the bookcase shear walls at that end of the building.