55 Baker Street, London

The original 1950s building, located at 55 Baker Street, London W1, suffered from a restrictive floor layout that was unattractive to today's commercial clients. Initially the plan was to demolish the building. However, an engineering-led redevelopment solution significantly reduced demolition waste, avoided using tonnes of construction materials and reduced the construction programme by many months.

The main element of the solution was retaining the majority of the existing concrete frame and removing only the most constraining elements of the original building. This targeted demolition facilitated the provision of large expanses of new open plan office floor plates. The sympathetic insertion of new reinforced concrete frames and stability cores created three seven-storey atria that allow natural light to flood into the building. The redevelopment resulted in a 30 per cent increase in the floor area of the original building to 56,000m2 in total.

Using concrete for the infill structures, such as the new slabs, beams and columns, allowed the new structural elements to be easily meshed into the original concrete frame. Furthermore, the use of modern reinforced concrete materials and techniques allowed increased floor spans while maintaining the same shallow depth of floor construction.

With regards to the infill structures, further savings were made by the use of precast permanent formwork panels for the construction of walls and infill slabs. The use of the panels reduced site waste, reduced the number of vehicle movements to site and contributed greatly to the rapidity of the redevelopment programme.

In addition to the savings in resources, further sustainability benefits have resulted from the enhancement of the building's energy efficiency through the use of modern cladding systems and the adoption of chilled beams to provide heating and cooling within the offices.

The 23 new homes built as part of the scheme include affordable housing units. They are dressed with masonry façade to complement the existing mews streetscape. Their roofs are planted to offer improved insulation and to encourage biodiversity to the area.

The development has achieved the highest BREEAM rating of 'Excellent' and it stands as an important benchmark of what can be achieved when redeveloping an existing site. This is especially relevant when one considers the UK's increasingly ageing 20th century building stock. Adapting and extending the life of existing structures offers valuable sustainability benefits in terms of saving resources and energy.

The radical transformation of this dated 1950s concrete-framed office building into an important new urban location underlines the long-term sustainability of concrete construction. It demonstrates that the ability for a building to last and be able to change to meet new requirements is more important than fitting the latest environmental gadgets.