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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It's going to be another dry day with plenty of sunny spells and feeling humid. Highs of 27 deg C.
A castle in Suffolk's hosted its first ever medieval jousting tournament as calls are made to make it an Olympic sport.
A mainly dry day with some sunny spells in the morning, but turning cloudier during the afternoon. Feeling warm. Highs of 27 deg C.