Siptu members at GMC Civil and Mechanical Engineering are to go on strike after discussions between the union and the firm over pay increases collapsed.
The union confirmed on Tuesday that the "last-ditch talks to avoid an all-out strike of members" were unsuccessful, and the strike will go ahead as planned on Wednesday.
The union claims GMC has failed to deliver on a pay deal struck earlier this year.
"Our members never take the decision to strike lightly," Siptu's transport, energy, aviation and construction division organiser Adrian Kane said.
"However, the inflexible and disrespectful approach adopted by management has left them with no option. Something has to give."
He added: "At the talks last night to resolve this dispute, the company sought further extensive changes to work practices as the price for implementing a pay and productivity deal which they had agreed to in May.
"To stall for months and now, at the eleventh hour, attempt to foist massive changes onto workers in return for a modest pay increase is completely unacceptable."
The utilities company is contracted by Gas Network Ireland for the installation, maintenance and provision of emergency response on gas infrastructure for commercial and residential customers.
As a result of the strike, gas customers have been warned that some services may be impacted.
Pickets will be staged from 7am on Wednesday at GMC House in Millennium Business Park in Ballycoolin, Dublin 11; Red Cow Yard in Dublin, 22; Oak House Business Park in Bagenalstown, Co Carlow; Whitecross Yard in Cork; and Dock Road Yard in Limerick.
