The National Archives of Australia's Mitchell storage facility has become so decrepit that tape is being used to hold down floor tiles which could contain asbestos.

Federal Parliament's Public Works Committee heard evidence yesterday about plans for a new $92 million preservation facility to take pressure off the existing centre which is so full that it has been forced to stop accepting some classified documents.

Labor Senator Anne Urqhart noted during a visit to the Mitchell storage site that she had noticed at least one vinyl tile which could contain asbestos was being held down by tape and asked what plans were in place to ensure the safety of staff.

''You could almost build a house with that [gaffer tape] but we are dealing with quite a toxic substance,'' she said.

Archives assistant director-general Cheryl Watson said processes were in place to protect staff from exposure to asbestos.

''Staff are aware that it is there, they have a notification process for staff,'' Ms Watson said.

''We also have a contractor notification process. Where we bring in the contractors to do work in the archives we have an appropriate register and induct them in and inform them of the issue. And then we have an appropriate plan to limit what we do to the tiles as far as possible.''

Ms Watson said the archives had no room left for ''top secret'' classified documents but was still able to accept ''secret'' documents.''

''The records aren't at risk because what we do is work closely with those agencies and they are able to maintain them at their site until they are able to transfer them,'' she said

''In relation to secret classified material we have recently invested in upgrading one of our vaults to be able to take secret transfers for a longer period until the new building comes online.''

The current site had 10 kilometres of shelf space for classified material and the new centre would have an additional 20.5 kilometres of space for classified documents. In total, there would be 75 kilometres of shelving for paper records.

The Public Works Committee also heard evidence on plans by Defence Housing Australia for accommodation to house between 300 and 400 residents in Weston. The nearby Orana Steiner School had complained about not being consulted about the proposal.

Defence Housing officials told the committee the school had been consulted by ACT planning authorities about development of the greenfield site. Defence Housing also planned to consult with the school.