Interserve’s contract, awarded by the Welsh government, includes renovations to the ground and first floors of the hospital. Among departments to benefit are operating theatres, critical care, radiology and outpatients’ services.
The builders will be in until 2026 but the hospital will remain operational throughout.
Paul Gandy, managing director of UK Construction at Interserve, said: “Our excellent track record in delivering projects similar in nature to this one, means we are now considered one of the country’s leading construction companies for healthcare projects and we look forward to starting work and creating a modern and efficient hospital for the people of Merthyr Tydfil and beyond.”
This contract represents phase three of the hospital’s refurbishment. Willmott Dixon completed a £28m four-year phased ward refurbishment programme in 2012, three weeks ahead of schedule and under budget.
Phase two was a £25m contract for a new main kitchen, dining area and a new pharmacy, which Interserve is now completing.
Contract award for phase three follows approval last month from the devolved Welsh government for £220m funding for the hospital’s programme of works.
Wales health minister Vaughan Gething said: "This is a substantial investment which will enhance patient care and the working environment at the hospital. The hospital provides vital care for the Cwm Taf Morgannwg area and beyond, especially for a number of residents of Powys.
"Alongside the many health and wellbeing benefits this funding will bring, it will also provide an economic boost for the community through local labour and subcontractors."
Cwm Taf Morgannwg University Health Board chair Marcus Longley said: "This is excellent news. There are still several years of major work to take place in Prince Charles Hospital, and this investment gives that work new impetus. When it’s finished, we will have a hospital truly fit for generations to come."