The building concept masterplan, created in 2017 and obtained under freedom of information, shows the memorial wants to cater for more visitors and to remain relevant to future generations.

The plan shows artist's impressions of what the potential extension underneath the existing southern forecourt could look like, a new courtyard and gallery to the east of Poppy's cafe, and an extension to the Bean Building, which currently houses office space for memorial staff.

The presentation focuses on the constraints associated with the current entry to the memorial, including issues with accessibility. Expanding the entry is listed as one of three key issues to address for the future, along with telling the stories and connecting new audiences.

"Create a new concourse to increase capacity, improve access and expand operational flexibility,"is listed under the the key objective to expand the entry.

"A new concourse below the existing entrance will enable the memorial to manage increasing visitation," the plan said.

The plan said the expansion would involve building about 20,000 square metres of new space and refurbishing about 10,000 square metres of space, bringing the total floor space to almost 40,000 square metres.

The document also addresses the memorial's challenges around presenting more recent conflicts as well as keeping up with expectations around digital connectivity. It also mentions changing building standards.

"Building codes have changed over the past decade. These will need to be addressed without impacting the heritage value of the building and site," the plan said.

A spokesman for the memorial played down the significance of the draft documents.

"The information provided to The Canberra Times by the National Capital Authority came from initial scoping undertaken at least two years ago. It is preliminary, outdated and not reflective of where the project is currently placed," the spokesman said.

The War Memorial has been allocated $16 million by the government to develop a detailed business case for the expansion, which has been tipped to cost up to $500 million.

"The memorial is currently following the strict guidance of the Department of Finance for the preparation of detailed business cases for submission to government," the spokesman said.

"This business case is currently in development to be considered by government later this year; no decisions on design have been made nor further funds allocated to the memorial at this time."

The spokesman said consultation about the proposed redevelopment with stakeholders, including the public and the media, would start shortly.