The workers also expressed fears about jobs and the future make-up of management in the wake of O'Rourke's takeover.
One member of staff said: "Since the announcement, there has been a tension about the place, people have been gathering in corners, whispering and basically beginning to plot their next moves." Angry employees at Laing's head office in Hemel Hempstead, Hertfordshire, claimed that the group had shown little concern for the 2000-strong workforce.
One said: "It doesn't really matter to the management what the employees are feeling now the company is to be sold. The announcement came from the management via email.
"It was more important for management to inform the City first because of the effect it would have on the company finances and on the share price." Staff said the key issue for them was the role of Laing's construction chief executive Brian May.
May met O'Rourke group managing director David Anderson at the Hemel Hempstead office on Tuesday to discuss the deal. Staff said if May left, it would severely hit morale.
One insider said: "If May is left to run the business and reports straight to Ray O'Rourke, it might work. If Anderson is more proactive, there could be tension between them.
"It is not known whether Anderson will work from the Laing offices or what the extent of his management involvement will be." Anderson was seen as the key factor in deciding the fate of other members of management, insiders added.
One said: "The fate of many of the managers will now depend upon how they get on with him but I'm sure there will be departures." Another employee said: "Senior managers are the more likely casualties of the takeover and they could go soon if O'Rourke brings in sweeping changes from the outset.
"At the moment, the clever thing for any of the managers to do is not to walk out but to stay and negotiate redundancy payments.
"It is unlikely that the jobs of project managers will be on the line in the short term because they are the ones that make the company money and who know and liaise with the clients." Staff described the atmosphere at the head office. One said: "O'Rourke had a marching squad of lawyers and accountants entering the building and getting ready to tackle a massive pile of documents tied with red ribbons. It was slightly surreal." Some predicted that being taken over by a subcontractor would be a huge culture shock. "I don't think we'll be doing cartwheels," one said.
Other staff were more stoical.
One regional source said: "It's too early to say what's in store for us. We have a good future order book for the next two years, which is good for the staff. That's the best you can hope for." A source close to one senior manager said: "He was of the view that it's been a roller-coaster for the last two years and this is just another turn.
"He thought it would be good to get out of the group's hair. They have not felt loved for some time – wherever they were going to go it had to be better than the present state of affairs."