Costain is to merge with May Gurney.
Costain earned pre-tax profits of about £26 million on revenues o f£930 million in 2012. May Gurney had revenues of about £700 million in its latest financial year, earning profits of #19.3 million.
Costain's existing shareholders will take 53% of the enlarged company, with May Gurney investors taking 47%.
The deal still needs the backing of both sets of shareholders.