The family business, more than 150 years old, will team up with multi-disciplinary construction firm BESIX Watpac to build the $80.5 million St John of God Ballarat Hospital redevelopment, set to start on Tuesday.

This extends Troon's reach in the medical precinct with the company also taking on stage one works for the $541.6 million overhaul at Grampians Health's Ballarat Base Hospital next door.

H Troon director and fifth generation builder James Troon said his company already gad a strong relationship with the St John of God Ballarat Hospital project, having worked closely with the healthcare provider in the past decade.

"We are deeply committed to the local area and local trades and suppliers and look forward to leveraging the expertise of BESIX Watpac to build a new hospital building," Mr Troon said in a statement to media.

The expansion will create a new medical services building at the hospital's Drummond Street front. The project will add a 10-bed intensive care unit, four operating theatres, an expanded recovery room, a 30-bed in-patient ward and an upgraded catheterisation laboratory.

St John of God Ballarat chief executive officer Alex Demidov said H Troon was the organisation's builder in the hospital's 2008 expansion and it was "reassuring to come together once again" with a Ballarat partner for the next major redevelopment works.

"The joint venture is a perfect blend of local experience with national and global reach and we are looking forward to working with both H.Troon and BESIX Watpac to deliver the best possible outcome for the Ballarat community," Mr Demidov said.

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Redevelopment works will include the closure of the Drummond Street entrance until the project's expected completion by mid-2024.

St John of God Ballarat Hospital's main entrance will shift to be off Mair Street with a second entrance point on the hospital's Webster Street side.

Limited visitor parking and a drop-off zone will also shift to the rear of the hospital.

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