The existing building at Trinity Court was a 1990s façade retention of a listed façade on John Dalton Street in Manchester. The proposal was to infill the atriums at each floor and create a new single storey extension at roof level. We were fortunate to have a full set of structural drawings available for the 1990’s work and this meant that additional loads to the structure could be checked with confidence. The atrium space featured four 457mm diameter circular columns over the full height of the building. The new atrium infill structure could only be supported on these columns as the perimeter structure was too light to take any additional load. The form of the roof structure takes the loading back to the existing columns below. The roof had previously supported plant and could therefore take the proposed office loading without any strengthening.