Mr Matthews inspected progress on the double-bunking project at the Milburn facility during a visit yesterday and said he was pleased with how the project was going.
An extra 122 beds are being installed to lift prisoner capacity from 335 to 485 to meet the forecast rise in national prisoner numbers.
All work must be complete by February next year, but the department is still waiting to get clearance from the High Court, which is hearing an application from the corrections officers' union to delay the project, citing staff safety concerns.
Mr Matthews said he believed prison staff were "more than happy" with the double-bunking concept.
When asked if other forms of prisoner accommodation were being considered, he said the new double bunks were all that was planned for now.
Shipping containers were options for other facilities, but there were no plans "in the future" for containers to be used at Milburn.
"Maybe in the long-term, who knows, but that's not the plan for here."
There was still plenty of empty space on the site for more buildings if needed, he said.
