Latitude/Longitude: 51.5035, -0.0806
The Tooley Street project is an 18,500 sq m mixed use development for Great Portland Estates. The scheme represents a significant step forward in the evolution of office design embodying current thinking about how commercial buildings need to respond to the issue of sustainability, in its broadest sense. Part refurbishment and part new build, the project offers six floors of flexible, speculative office space, a variety of retail units on the ground floor and five residential units.
The ‘Lean Office’
From inception, the client and project team wanted to design a building that would serve as a new model for large scale commercial office developments. The ambition was to create a high quality, flexible product that embraced sustainability and the use of intelligent procurement and construction. An innovative approach was adopted for all aspects of the building’s design, procurement and construction. All of these can be loosely defined under the term ‘lean office design’. Whilst few of the technologies applied are in themselves ground-breaking, it is the way in which these have been successfully brought together, coupled with the scale of application that was visionary.
The commitment of a forward-looking client was pivotal to the outcome of this process. The development of a new office model, combined with the use of untested building techniques made this a more risky venture than most. The success of the product, and by implication the process that led to its development, is borne out by the fact that the building was forward sold prior to work starting on site and has subsequently been fully let to a single tenant.
The ambitious targets for the scheme were attained through the collaborative approach adopted by the wider team throughout the life of the project. Intelligent procurement and construction methods included the early input of specialist knowledge regarding the external envelope, exposed superstructure, and buildability; a 2-stage tender and incentivised pre-construction services agreements with key sub-contractors. The input of Laing O’Rourke, the main contractor, and their in-house subsidiaries – as well as specialist sub-contractors, particularly Schneider (cladding and barrel vault roofs), was invaluable to this success.
Form and Façade
The building occupies a dense urban site on the south side of Tooley Street in Southwark. The form and mass of the building have been derived from an analysis of daylighting and rights of light as well as a consideration of the characteristics and scale of surrounding buildings. The barrel vaulted roofs are a direct response to the rights of light envelope developed with Anstey Horne. The idea was to maximise the internal volume, minimise the area of the cladding, whilst creating an interesting spatial experience and an identifiable external form.
The principle organising device in the scheme is an internal street that accommodates the public areas of the building as well as the principle vertical circulation and services zones. The floorplates are arranged as two wings to each side of the street, having a depth of 19.5m. Natural daylight penetrates these spaces from the fully glazed internal elevation to the atrium and rear courtyard and the large picture windows in the external facades. Broad connections are made between these spaces to provide continuous donuts of lettable floor.
A light touch approach has been adopted for the refurbishment of the existing buildings, whilst providing a level of quality that is comparable with the new build office space. Externally, little has been done to these buildings other than a programme of repairs. Crucially though, the fenestration has been replaced to all buildings, giving a lift to their appearance and a hint of the new development behind. The lower floors of the refurbished buildings accommodate restaurant, bar and retail uses providing an active edge to the street.
Materials and Making
Achieving the project ambitions – for a high quality, flexible product and a low energy building – demanded a close integration of architecture, structure and building services. In employing an exposed soffit as an important part of an effective displacement air conditioning system, the engineering solutions become the architecture and control of the finish therefore became crucial.
The precast concrete soffit panels, or ‘biscuits’, were formed in steel moulds using self-compacting concrete, with an as-struck finish. These are used as permanent formwork to a post-tensioned in-situ slab and have steel lattices cast into the top surface to tie the construction together. The logic applied to the soffit was extended to other aspects of the superstructure. Structural elements in the two main cores are of fairfaced concrete, using steel formwork and strongbacks to largely eliminate the need for tie bars. The central columns act as structural ducts delivering cooled air from the rooftop plant, directly to the perimeter zone of each floor plate, where the solar gain load is highest. The development of techniques for pre casting these components involved a high degree of coordination between the manufacturer and the team.
The design and construction of the barrel vault roof adheres to the stated aims of producing prefabricated, repetitive components in controlled off-site conditions, which are then brought to site for assembly. Structural extruded aluminium ribs infilled with identically sized solid and glazed overlapping units were prefinished internally and externally. A timber lining system softens the appearance of the anodised aluminium panels and provides a visual link with the finishes to the cores. Other prefabricated finishes to the interiors include the timber veneered and white finished joinery panels as well as high level GRC units within cores and to the double height barrel vault space on Barnham Street.
The absence of lightweight finishes to ceilings and walls meant that there was no opportunity to conceal building services. This led to the development of a bespoke lighting system in conjunction with Zumtobel, with integrated fire protection, whilst the floor void acts as a plenum for the displacement system and also contains distribution for small power and data.
A driving ambition of the project was to achieve a BREEAM Very Good rating. Throughout the design development alternative strategies for sustainable design were considered and solar gain was addressed through the form and façade design. Significant use of prefabricated components delivered a number of advantages including; a greater guarantee of quality and finish: the reduction of on-site work and the need for site storage; reduced reliance on wet and finishing trades; reduced waste. In addition to this, a rain water harvesting system was incorporated into the scheme.
After planning permission was granted in 2005, the GLA’s requirement for 10% of the building’s energy consumption to be provided from on-site renewable sources became mandatory. The inclusion of a biomass boiler as well as solar thermal preheating of hot water, using evacuated tubes on the west facing roof were able to provide a total of 10% of the building’s energy use.
Client: Great Portland Estates PLC
Structural Engineer: ARUP
Building Services Engineers: ARUP
Project Manager: Jackson Coles
Main Contractor: Laing O’Rourke
Quantity Surveyor: Gardiner and Theobald LLP
Planning Consultant: Montagu Evans LLP
Rights Of Light Surveyor: Anstey Horne
Fire Consultant: Bodycote Warringtonfire
Approved Inspector: Butler and Young Group
Planning Supervisor: Gardiner and Theobald LLP
Party Wall Surveyor: Jackson Coles
Acoustic Consultant: Alan Saunders Associates
Letting Agents: DTZ Holdings Plc
Contributed by Allford Hall Monaghan Morris
⇒ Architecture Guide to LONDON