The 208,000 sq-ft (18,720 sq-m) supershed building at Stratford Market Depot for the London Underground’s Jubilee Line Extension has won several major awards. The unique design of the train maintenance building (which can hold up to 11 trains at one time) was influenced by the tracks, site restrictions and architectural considerations and features a strong emphasis on natural daylighting. The southern elevation is clad with a translucent Kalwall Curtainwall. Now five years later, the facility was visited and assessed by the Underground’s own architect, Peter Bradley. His comments follow: “The building is a very large, open building – housing the maintenance depot for the London Underground trains. The south elevation of the building is clad almost entirely in Kalwall. The material externally appeared to be in excellent condition, in spite of not having been cleaned at all, with no visible dirt on the surface. The surface had a slightly shiny appearance externally, while the internal face was more matt. "The internal view is impressive, in that no glare was evident, but a substantial amount of light penetrated to give an even, shadowless light inside. Externally, the supporting structure and a variety of services located close to the cladding on the inside were not visible, so services could readily be run on the inside without spoiling the external appearance. “The standard Kalwall skin was tough, made from fiberglass, but treated to combat ultraviolet degradation. Certainly no deterioration was visible, in spite of 5 years of exposure on the south-facing elevation … Panels can be repaired if serious damage occurs.” “The engineer who showed us around said that they had not had to carry out any maintenance on it, nor had they had any water leaks. He felt it was a good and serviceable product.”