The new Cwm Rhondda hospital was due to open last autumn but the underfloor heating system has caused floor tiles to buckle with floor temeratures reaching 40C.
Cardiff-based Cowlin Construction, which made 68 staff redundant earlier this year, declined to comment.
However Cwm Taf NHS Trust confirmed theat it had commissioned an independent review to look into "apparent defects". Repair work could take until next spring to complete.
Sources say the flooring was laid without sufficient expansion joints to cope with the state-of-the-art, environmentally friendly underfloor heating system.
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Conservative health spokesman Andrew Davies said: "It could be next spring before this problem is made right - and that may mean money has to be spent on the antiquated hospital where patients are being treated in the meantime."
The hospital will have 100 rehabilitation beds, an eight-bed stroke unit, an outpatient department, minor injuries unit and an integrated primary care centre.
David Lewis, director of finance at Cwm Taf NHS Trust, said: "We have had practical completion of the hospital and there are apparent defects in the flooring.
"We have commissioned an independent review to determine whether there are defects and, if so, what remedial action needs to be take.
"We will have this report by the end of the month and we will then know what the next step will be."
Cowlin Construction Cowlin was acquired by Balfour Beatty in 2007 as part of the firm's plan to expand into South Wales.
