Sydney’s Australian Museum has unveiled a AU$285m(US$214m, €201m, £168.6m) masterplan proposing a new multi-storey extension to stretch over the top of its existing building in the largest redevelopment in the institution’s 189-year history.

The Barrabuwari Muru (future path) masterplan by Hames Sharley places a new extension in the museum’s eastern quarter, an area currently taking up a car park and storage facility.

The 2,700sq m (29,000sq ft) extension and wider redevelopment will more than triple museum floorspace, up from 6,500sq m to 20,000sq m, allowing the museum to exhibit as much of 20 per cent of its 18 million-strong collection of artefacts – an increase from the current 1 per cent.

The new masterplan envisages a great hall at the site’s centre. Created by removing existing buildings between heritage-listed parts of the museum, the 70 metre-long hall could accommodate up to 2,000 people at one time.

A large new space for temporary exhibitions would also be created, “allowing Sydney to compete on the global stage” in terms of international blockbusters.

In preparation for the masterplan, the museum has commenced an extensive transformation programme to upgrade existing facilities including its Crystal Hall opened last year; a new First Australians Gallery featuring two new permanent exhibitions; the Pacific Spirit Gallery; a new rooftop restaurant; and the restoration of the Long Gallery – Australia’s first museum gallery – reopening as the Westpac Long Gallery in late 2017.

In addition to a reimagining of the existing space, the museum will create new education and community facilities, including new learning spaces, a theatre, an Indigenous and Pacific cultural centre and new DNA labs.

The masterplan has been submitted to the NSW Government for consideration as part of the State Cultural Infrastructure Strategy. An architect for the project is yet to be appointed. The museum – originally designed in 1857 by architect Mortimer Lewis – is planning to hold a international design competition for the new building held over two stages. Once approved, the museum is planning to start construction on the new building in 2018m with the extension to be open by 2022.