According to the Kohn Pedersen Fox Associates (KPF) office in London, England, the goal for the project was to use natural materials, including stone and wood. In order to meet the desired aesthetic, slate from Kirkstone Quarries of Ambleside, Cumbria, UK, was selected for various elements of the building.
The architects desired a dark green hard-wearing stone, which could be used for both indoor and outdoor applications. After visiting Kirkstone Quarries, Sea Green slate was selected. â€œThe color is intended to match the verdure of the adjacent exterior courtyard garden and parkland,â€ said Kevin Flanagan, the Senior Associate Partner and Project Architect with KPF. â€œThe flamed finish produced a ripple effect comparable to the adjacent water feature.â€
Over 30,000 square feet of Sea Green slate were used for both interior and exterior applications, primarily on the ground floor and all typical elevator lobbies. In addition, slate was used for the main reception desk, office credenza tops, column and external skirting and landscape seating.
For interior applications, slate was used as 24 x 12 x 1â„2 -inch tiles. Similar sizes were featured on the exterior, but a variety of thicknesses were used.
On the external vertical cladding, Indiana limestone with a rough shot sawn finish was used to complement the slate.
According to the architect, the design was easy to implement. â€œStones were of a standard size, consistent in color and texture, and matched well -- therefore [were] interchangeable,â€ Flanagan said.
The stone flooring was installed over a three- to four-month period using sand cement, which is a typical method used in the region, according to the architect.
Nick Fecitt of Kirkstone said that although the stone was correctly specified, the dimensions of the stone was subject to negations. â€œThe size and the thickness were reduced at the architect's suggestion,â€ he said.
Construction of the building began in April of 2001 and was completed in September 2003. The De Hoftoren received an International Highrise Award and the European Nepix Award in 2004, and is a finalist in this year's ULI Award for Excellence.