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.
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A very windy and wet night in store this evening with gales- some severe on Sunday.
A group of kind-hearted mums from Northamptonshire have launched a campaign to try and help older people living alone in their community.
Winds will strengthen this weekend with outbreaks of rain at times later Saturday and into Sunday