The contractor has told staff that temporary pay cuts during April, May and June will now be returned in a bumper pay round next month.
The surprise announcement comes as all staff are also returned to full salaries in the UK.
An insider told the Enquirer: “This is great news for everybody. Its been a tough few months and this is a real bonus for us.
“We were told the repayment is recognition for the huge effort and commitment of our people during the crisis.”
Sisk is the first contractor to take the step of reimbursing wage cuts as impact of coronavirus on the business becomes clearer.
The firm was one of the first to announce a round of 50 jobs cuts as it took part in an industry-wide slimming down.
In 2019 financial results published last month, Sisk chief executive Steve Bowcott, said: “At this time, we estimate that the main financial impact of Covid-19 will be to defer some revenues from 2020 into 2021 due to the temporary closure and/or slowdown of live construction projects, particularly in the Irish market.
“The group has a strong capital structure with high levels of un-committed cash and no bank debt.
“As a result, the board believes that the group is currently well-positioned to deal with challenges Covid-19 might have on its activities.”
Across the Sicon Group – parent company for all of Sisk activities in Ireland, UK and overseas, turnover grew by 19% to just under €1.4bn, with pre-tax profit up 10% to €31m.
The UK business raised revenue a third to €728m.