Latest results from the firm show turnover at the Specialist Contracting Services division fell to £258.5m for the year to October 31 2018 from £295.3m last time.
The division offers demolition, groundwork, piling and structures design on a “one-stop shop” basis often direct to clients.
Keltbray said this year would also see a drop in demolition and civils work “primarily due to a slowing in new, early work opportunities.”
But it added: “This reduction will be more than offset by an increase in turnover at Keltbray Structures Limited, the reinforced concrete frame business.”
Keltbray also said it was looking to expand further in the rail sector following the acquisition of SPIE’s overhead power line business last year.
It said: “The group workload mix is changing to include more residential and infrastructure projects over and above the more the more established commercial base load.
“The group is also reviewing opportunities in other construction related market sectors and overseas to improve diversification and maintain turnover growth.”
Latest results show group turnover fell to £399.2m from £417.5m last time with pre-tax profit dropping to £17.8m from £23.7m.
Brendan Kerr, CEO of Keltbray Group, said: “I’m pleased with the progress made so far by our diversification strategy to maintain controlled and profitable growth.
“Our efforts have resulted in a good spread of turnover among our companies during the 2017/2018 period with the growth in both reinforced concrete structures and power stations decommissioning helping to offset falls in our traditional markets.
“We remain committed to our specialist contractor roots and the continuing investment in our self-delivery model.
“To employ, manage and train our own employees using our own specialist plant and equipment means we have a mitigation strategy to meet the challenging conditions we currently find ourselves operating in.
“We are contemplating further acquisitions to continue our diversification strategy and our directors are optimistic of continued revenue growth in 2019.”