Restoration of the Christchurch Town Hall has exceeded its budget.

Work is now expected to cost $152.2 million, up from $127.5 million.

The city council's Capital Delivery Manager for Major Facilities Alistair Pearson says they've taken the chance to modernise the building as it was built.

He says there have also been problems with the repair and strengthening.

The budget has been adjusted to take into account inflation costs, and to cover the costs of additional facilities for the Christchurch Symphony Orchestra.

The Town Hall is due to open in March 2019.