The £2.5m sale folowed a brief period where Bell & Webster was placed in administration before bieng acquired by FP McCann.
All employees at both firms have been transferred over to the new owner.
The sale means Eleco can now concentrate on its international construction software business.
Turnover at Bell & Webster and Milbury last year was £9.06m with the firms making a pre-tax loss of £1.74m.
John Ketteley, Executive Chairman of Eleco said: “We are pleased to have found in FP McCann, a highly regarded and successful precast concrete specialist in the UK and Northern Ireland, with a breadth of operations and capabilities that will enable our former precast interests to be integrated into a larger scale precast business.
“Our skilled and experienced workforce will now become part of FP McCann’s workforce and I would like to thank them for all their efforts and contribution to Eleco, while they were part of the Eleco Group.
“I would also like to thank John Stothard and Carol Lound for their outstanding leadership and service since they became respectively Managing Director and Finance Director of ElecoPrecast in a very difficult market”.
“The disposal of our former precast concrete interests eliminates an activity that had a lack of visibility of future performance, required major capital investment and generated substantial losses in recent years in very hostile market conditions.
“The divestment also represents the last stage in the transformation of Eleco from a Group dominated by loss making and capital intensive construction and building products companies, into a Group that is now wholly populated by consistently profitable, cash generative and growing construction software companies based in the United Kingdom, Sweden and Germany.”