This historic landmark on Leicester Square required revitalising so as to enhance its external appearance whilst maximising internal floor space within the constraints of the existing retained Grade 2 listed facade. Make Architects produced a design which included the construction of a two storey basement and the addition of an extra level to produce a mansard style roof.
The requirement was for a flexible yet robust structural waterproofing design in accord with BS8102:2009 which was supported by the appropriate design and system warranties. FIS were able to provide a strategy within the budget constraints which exceeded the clients requirements whilst ensuring practicability of installation.
The waterproof layer beneath the basement slab incorporated a combination of a bentonite membrane and a crystaline cementitous coating to the top of the pile caps to provide full protection. The risks associated with this deep basement structure demanded the use of a maintainable waterproofing system to manage any water ingress through the walls; therefore a cavity drain membrane was installed to the thoroughly prepared secant pile basement wall with a maintainable conduit installed at the base. Particular attention to detail was then required to provide continuity where the new structure interfaced with the existing retained structure.