Firefighters are tackling the blaze at Leggat Plant Limited on Blackbyres Road in East Renfrewshire.
The incident was reported about 4:45am.
No casualties have been reported from the fire.
Nine fire appliances were sent to tackle the blaze.
The fire is believed to be under control.
A cordon remains around the building.
Images of the fire appear to show the roof of the firm’s building has partly collapsed.
The blaze has caused a power cut to the Barrhead area. ScottishPower are working to restore the connection.
Leggat Plant Limited hires out cranes and heavy lifting machinery to the construction industry and has been running for 140 years.