One side of Canberra’s historic John Gorton Building has been completely hidden by a protective covering as the Finance Department undertakes urgent repairs to its crumbling sandstone facade.

Despite an October report finding a critical risk to users of the building from falling stone debris and lead capping, funding for repair and restoration works have only been allocated for the north-west facade.

Finance Department staff said this week poor air quality and inadequate toilets were hampering their work during the restoration.

Some have even resorted to bringing their own desk lamps to work because of darkness.

A statement provided by the Finance Department on Tuesday said the protective hoarding, which has been constructed in recent weeks, was now complete.

“The scheduled completion date for the repairs to the north-west facade is mid-2014,” it said.

“The fencing and hoarding will be progressively removed as facades are completed.”

Building restoration firm HBS Group has been engaged to complete the first stage of the works, at a cost of $2.1 million.

Additional funds will be spent on the replacement stone panels, to be paid to the firm on a reimbursement basis.

The scaffolding and hoarding will be removed progressively as repairs to all sides of the building are completed and the safety risk is eliminated.

The scaffolding in place has been sealed as a protection during the removal of small amounts of asbestos from joining work between the stone panels.

Repairs to the remaining three facades can’t go ahead without additional funding from the federal government.

Built between 1927 and 1956, the October report found materials had been collected after falling from 16 of the John Gorton building’s 100 wall surfaces.

It said an estimated 4 per cent of the 24,000 panels need to be replaced, while 10 per cent are in need of repair and some posed potentially ’’catastrophic’’ risk, including causing death.

Community and Public Sector Union director Beth Vincent-Pietsch said departmental staff needed more information.

“As if widespread job cuts wasn’t enough, now staff are having to come to work with their own lamps because it is so dark, the toilets are often closed and water and air quality is deteriorating," she said.

‘‘Most people understand that work needs to be done but they feel frustrated that it has come to this."

She called for briefings on any health risk for those using the building.

‘‘The Finance Department should never have let it fall into a state of disrepair and now it is the taxpayers and the staff that are having to pay the price,’’ she said.

Work is expected to continue until at least 2016.