The cost is now estimated to reach $50 million, up from the original $40 million price tag in 2009 to renovate the building in St. John's.
Works Minister Paul Davis says the renovations include the replacement of windows and brick, and repairs to the roof.
He says leaks in the building have caused brick and limestone to crumble, and at one point the government considered replacing the building.
The work is expected to be completed by the end of 2014.
Davis says it is the first major overhaul since the building opened in 1960.
When it opened, the province's website says the building had 675 rooms and housed every government department, board and commission.