Work began on the $160 million expansion of Canbera's justice precinct in March 2016, with stage one due in late 2017 and stage two in late 2018.

But documents tabled in the ACT's parliament on Thursday show project managers Juris now expected stage one to be completed in late August-September, and stage two in the first half of 2019.

However the "overheated" state of the construction sector in eastern Australia means there could be further delays, they warned.

"The court has been kept fully appraised of the delay and has taken this into account when listing matters in 2018," the report presented by ACT Attorney-General Gordon Ramsay said.

"During the construction phase for the new facilities the court has retained use of the same number of courtrooms (both jury and non-jury) as were available prior to commencement of the project.

"The main operational impact of the stage one delay is that completion of this stage will provide five jury courtrooms in place of the three that are currently available."

However because of the David Eastman retrial in mid-2018, some jury trials may need to be held in the Queanbeyan courthouse from June 8 to July 2017.

"The court is investigating the availability of the Queanbeyan courthouse for the central criminal listings that commence on September 17, 2018 to ensure any disruption is minimised in the event that the new courtrooms are not available by that date," the report says.

Juris is a consortium comprised of Laing O’Rourke Australia Construction, Macquarie Capital Group Limited, Programmed Facility Management and Lyons Architects.

The courts project was the ACT's first public-private partnership, with Juris expected to maintain the building over the next 25 years.

The ACT will pay the building off over that time, with the total project net cost put at $250.4 million in 2016 dollars.

According to the contract, Juris assumes full risk for the time it takes to complete the works and is not entitled to any extra payments if the project is delayed.

"This results in a saving to the territory compared to the payments that would have been made had the project been completed on time," the report to the Assembly said.

"These savings are greater than the project management and other costs incurred as a direct result of the prolonged period of construction."

Canberra's courts have suffered from overcrowding over the years, causing headaches with juggling juries. The Supreme Court was severely out-of-date, with issues playing CCTV and pre-recorded evidence, and problems with video links to remote witness rooms.

The new Supreme Court will occupy the four-storey building under construction on Vernon Circle, and also a reconfigured section of the existing Supreme Court building.

It will include eight courtrooms - including five jury courtrooms - and has been designed to accommodate up to 10 courtrooms - including eight jury courtrooms - in future.

The refurbished Magistrates Court will have 11 courtrooms, all with audio-visual and remote witness capabilities. It will also have one new hearing room.

The new precinct will also have a new and expanded custodial facility, dedicated vulnerable witness suite, new mediation suite, dedicated parole board hearing room, and new jury facilities.

A new public entrance and registry area will be built in the open space between the two existing buildings, connecting the Supreme and Magistrates Courts.

Stage one of the project includes the new four-story Supreme Court building, the Magistrates Court building refurbishment and the new entrance foyer linking the two buildings. It includes six new courtrooms, five of which are equipped for juries.