For them the exterior "represents an evocative confluence of various Parisian architectural traditions"; the Piccadilly arcade echoes the arcaded ground floor in the Place Vendrome and the Rue de Rivoli, the steep mansarded skyline on the Green Park facade echoes Hector Lefuel's work on the Pavillon de Flore of the Louvre, while the tall windows and wall panels of the facades resemble those of Mewès's earlier work on a smaller building made as a home for Jules Ferry on Rue Bayard. Excavation for the hotel began by contractors Waring White Building Co. Ltd in June 1904, and it was completed by 1 October 1905, and opened the following May. The building progress was documented each month by The Builder's Journal and Architectural Engineer, and in one edition noted the difficulties of some of the aspects of construction such as hoisting 20-ton steel joists in a narrow building site. The Architect and Contract Reporter noted that the limited space did not allow for the storage of materials on site. All mortar had to be mixed in the basement and the stone was dressed "on a platform with a watertight roof over the footway". The red-brick foundations of the earlier Walsingham House had to be blasted away to facilitate the foundations of the steel structure in concrete. The total estimated cost was £345,227. 8s. 1d., with £102,000 going to Messrs Waring and Gillow, £49,000 to French decorators and over £15,000 to the English decorators. John P. Bishop and the Swedish-born Sven Bylander were consultant engineers during the building phase. The facade on the Piccadilly side is roughly , on the Arlington Street side, and on the Green Park side. The irregularity of the site presented initial problems for the builders. Davis dealt with this by "brilliant perspective effects" according to Binney, using curving walls to "cleverly conceal the rapidly diminishing space at the back of the hotel". The purpose of the arcaded front was to provide more space for the bedrooms above. Expensive Norwegian granite is the material on ground floor, with Portland stone above it. The steel frame of the building was made in Germany and is based on a model made in the early 1880s in Chicago to increase fire resistance. It was erected by Messrs Potts & Co. of Oxford Street. Fireproofing of the walls were conducted by the Columbian Fireproofing Company Ltd. of Pittsburgh and London, with steel-ribbed