Balfour Beatty finance chief Duncan Magrath is quitting just over a month since the civil engineer issued its fifth profit warning in two years.The FTSE 250 group, which fought off a takeover bid from rival Carillion, said the hunt for a new chief financial officer (CFO) will begin soon, with Magrath remaining on the board and as CFO until his successor has been identified.The company has appointed the former boss of defence group Qinetiq, Leo Quinn, as its new chief executive after Andrew McNaughton left the role in May, with chairman Steve Marshall taking over.Marshall has said he will step down from the board once a new chief executive and non-executive chairman have been appointed.Magrath, who has been CFO for the last six years after joining two year before as deputy finance director, is expected to leave the business in 2015.Marshall said: "Duncan has been our CFO for six years. He has shown huge personal commitment to Balfour Beatty, and particularly in the recent more challenging times, his contribution and his resolve under pressure has been unwavering."Following the completion of the Parsons Brinckerhoff disposal and the announcement of our new group CEO, Duncan will be seeking new career challenges in 2015."