On Monday night Southwark Council approved a planning application to build a new 'loo with a view' and art gallery next to the six-year-old building, which Alsop designed with ex-partner Jan Stormer.
The 'landmark' 10m-high public lavatory cubicle at the centre of the single-storey scheme, which the library has dubbed the Peckham Pier project, will be made from Cor-Ten steel.
Painted purple, the loo will have a little surprise up its sleeve - unobstructed views of the sky.
Next to this central 'sculptural' unit, there are plans for a new painted-timber art store and an exhibition space which can be opened up onto the timber-deck platform.
The gallery, designed under the recently-formed SMC Alsop banner, is expected to host a varied mix of 'high quality fine art and design', from Turner-prize winners to local artists.
The council's executive member for regeneration, councillor Richard Thomas, said: 'This latest addition brings space for art, culture and entertainment to Peckham's already vibrant and diverse community.'