To insulate the building, it was constructed with brick walls and had no windows above the first floor, except in the stairwell. The interior walls were covered with layers of cork impregnated with tar, polystyrene foam and polyurethane to improve insulation. The insulating layers were up to thick. Two elevator shafts ran alongside the stairwell. The first and second story floors were constructed of concrete, and those above were constructed of timber. In 1912, the building was extended on the west side. The extension almost doubled the floor space and included two further elevators serving all levels, a second stairwell which terminated at the 3rd floor, and some windows in an office space on the north-east corner of the 2nd floor.