Both plants in Creetown and Killoch are being closed.
The company blamed tough trading conditions in the construction sector.
Barr began a review of Solway's future last month, but has taken little time to reach a conclusion. Staff are being consulted with a review to redeployment elsewhere across the group.
The decision to close came even as the company was at a critical stage on Tollcross Aquatic Centre's new extension for the 2014 Commonwealth Games swimming events. On 20 December Solway erected the main 78m-long 152-tonne steel truss that supports the roof. This box-section truss, fabricated at Creetown, was even larger than the one that Solway had previously delivered and lifted into place at Ryanair's maintenance hangar at Prestwick Airport.
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