Richard Skan, a director at Bowsprit, said the company aims to reach a similar level within five years.
He added that Bowsprit had been "run down" by AEA, which wanted to focus on the mechanical and electrical engineering side of ERG. Bowsprit specialises in concrete repair and employs up to 20 people.
Skan said: "We were a small civils arm of ERG. We weren't allowed to go for the work we wanted."
The four directors at Bowsprit believe they can make the company more competitive, as it won't suffer the overheads of a big company. ERG's overheads were shared evenly between companies in the group, leaving Bowsprit over-burdened given its relatively small size.
Bowsprit would not disclose the value of the buyout, but employment conditions, such as medical costs and redundancy pay, were included in the purchase price.