We were familiar with this building, as managing director (India) Mukesh Pritamdasani and his team designed the original structure while working at Ramboll. The Mall is composed of two basement levels — for parking and building services — retail units at ground and first floors, and two further levels of multiplex cinemas and food courts. A flat slab and drop panel system was adopted for the frame, founded on good quality hard rock, with service cores and peripheral frame elements resisting lateral loads. However, the possibility of additional floors wasn’t considered at the time.
The extension covers almost 90% of the area of the flat roof, and required the relocation of various plant installations. The new structural work had to minimise the need for strengthening the existing frame. In addition, the Mall was to continue to operate as usual during construction. Extensive site survey and analysis was carried out with Lodha’s team and the contractor to locate the load transfer points. It was determined through calculations that a steel frame with roof sheeting was the best solution, given its high strength-to-weight ratio, and a detailed construction sequence developed that avoided interruptions to building operations.
The graded waterproofing on the existing roof was removed, revealing the flat slab below. Cut-backs were made to allow for the installation of staircases and and a small hydraulic lift from level 3. A system of steel trusses was constructed, on cranked perimeter columns plus an internal column grid, placed directly over existing concrete columns below, wherever possible. For the few places where this was not possible, the slab has been stiffened. The structure is clad in sandwich sheeting, with exterior stone and timber finishes matching the original building, so visual unity is achieved.
GROSS EXTERNAL AREA (existing mall) : approx 650,000 sq m
GROSS EXTERNAL AREA (extension) : 2,500 sq m
Kalyan Shil Road, Palava, Thane, Maharashtra, India
other images : Whitby Wood Pritamdasani