Trex brings additional US manufacturing online Trex Co. Inc. Trex has completed an expansion of its Winchester, Va., plant, adding more capacity for its growing decking business. Composite decking manufacturer Trex Co. Inc. opened 200,000 square feet of manufacturing and support facilities next to its headquarters in Winchester, Va., capping off a $200 million expansion program that increased capacity by 70 percent in about 18 months. The extruder of recycled polyethylene and wood fiber decking announced in June 2019 that it would add production lines in Fernley, Nev., and build the Winchester facility to meet increased demand for low-maintenance products that enhance outdoor living spaces.