The target was originally set by chief executive boss Leo Quinn eight years ago.
Latest results for the contracting giant show the UK business boosting profits as the American operations racked-up a loss due to a problem civils contract in Texas.
Results for the six months to June 27 2025 show an overall pre-tax profit of £132m from £112m last time on turnover up to £5.1bn from £4.7bn.
The UK construction business saw its profits from operations increase to £56m from £34m on revenue of £1.56bn from £1.46bn.
Balfour said: “UK Construction achieved its long-standing margin target of 3% in the period, with strong project delivery, the improved risk profile of its portfolio and a one-off £10m insurance recovery contributing to underlying profit from operations of £56m.
“This represents a 3.6% PFO margin. The full year PFO margin for UK Construction is expected to be around 3.0% prior to including the insurance recovery.”
The UK Construction order book grew by 2% to £6.3bn and support services increased profits to £46m from £34m on revenue up to £662m from £554m.
Quinn said: “Our continuing strong cash generation is underpinned by a growing order book with improved margins and lower risk contract forms.
“This provides the Board with increasing confidence in significant future cash generation that supports our ongoing dividends and share buybacks. This is demonstrated by the momentum in our key growth areas in the first half.”