Costain and May Gurney have announced merger plans.
The companies will have combined revenues of £1.6 billion and challenge rivals including Balfour Beatty and Carillion.
Major infrastructure contractor Costain, which is working on London's Crossrail underground rail tunnel, is based in Maidenhead, which will be the group's headquarters.
The group plans to retain May Gurney's headquarters in Trowse, Norwich, as a shared services base.
May Gurney has around 800 of its workforce in Norfolk.
More top news
As the nation gears up for the biggest sports day, a boxing club in Peterborough has opened its doors for young people to sign up.
After a dry night, there's a risk of thundery downpours both on Saturday and Sunday. Monday will be the best day of the Bank Holiday Weekend
Ipswich Town manager Mick McCarthy is itching for his side to return to their dominating form against Preston this weekend.