But as costs rose from safer working restrictions, operating margins were squeezed to 0.7% from around 1% previously.
This saw pre-tax profit almost halve to £2.8m in 2020 from £5m the year before.
Strong cash management saw cash at bank nearly double to £62m from £32m with net assets at £11.3m.
During the year, the Sisk received nearly £1m from the Government job retention scheme, helping to maintain UK staff numbers at 594.
In a statement alongside the accounts, John Sisk said it now enjoyed a strong pipeline of work with a strong order book covering this year and a good line of sight for 2022.