A lightweight concrete and Bondek permanent shuttering system formed the basis of a tied-in roof between an existing structure and a new addition on this shopping and office mixed use building on Gwen Lane in Sandton. A lightweight concrete with a density of no more than 1200kg/m3 and a compressive strength of 12MPa was specified and a preblended CemteQ 1200D lightweight concrete was supplied in bags for ease of handling.