The Cheshire-based practice plans to increase the floor space of the empty 1960s office block from 3,570m 2to nearly 5,700m 2by extending the lower storeys out from the facade.
The eight-storey building on the corner of Victoria Street and Crosshall Street will also be given a new 'sculptural' roofscape, which is intended to 'float as a separate element' above the existing structure.
Describing the design of the roof, a spokesman for the practice said: 'The varying contours and organic silhouette of the mesh relates to the corner turrets and dormer windows within the roofscapes of the adjacent buildings.'
As well as creating 18 car-parking spaces in the basement, the scheme for developer Huntsmere Tinlings will also boast rooftop photovoltaics, a grass roof and wind turbines.
The development is expected to go before Liverpool City Council's planning committee on 12 December and could start on site early next year.
Meanwhile the firm is also redeveloping the neighbouring site - a mixed-used project which includes the refurbishment of a Grade-II listed church.