Contractors at Knox race against time

Contractors working on an $11.3 million earthquake-strengthening and extension project at Dunedin's Knox College are in a race against time to get it finished before students return next year.

Work began on Monday, with up to a 120 people working at the site each day. The contractors were getting to work as students at the residential college were moving out.

The work was triggered after the main building at Knox was found to be "earthquake-prone".

It includes an addition to the number of rooms at both Knox College and Salmond College to help repay loans for the work.

Project manager Sam Cadden, of Arrow International, said 95-120 people were working on the project, 12 hours a day, six days a week, to get it finished in 10 weeks. It was "by far the largest" refurbishment the company had worked on in Dunedin and that it had to be completed in such a short time made it particularly difficult.

"We are extremely confident [it will be finished on time], but with a building of this age, you really don't know what you are going to uncover." One of the challenges was being able to find the resources in Dunedin for such a large project, Mr Cadden said.

"To do almost an $11.5 million [project] in 10 weeks, especially over the Christmas period as well, is extremely difficult."

Bringing the building up to 2012 building standards included improving the fire standards and rewiring the building. Installing fire doors alone cost $800,000, he said.

It was hoped the work would bring the building to 75%-80% of new building standard (NBS) for earthquake strength.

Before the work began the 103-year-old main building was rated at less than 20% of NBS.

Any building rated less than 34% of NBS is classified "earthquake-prone".