Therma-Tru a door manufacturer at Treforest, near Pontypridd, is more than doubling its workforce with the creation of 150 jobs. A £7.5m investment in a new production plant will enable it to manufacture 250,000 doors every year for its Sentinel Doors firm. The project, backed by the Welsh Assembly government and the Welsh Development Agency, will begin in the new year. The plant, which currently employs 139 people, will also create a new research and development and technical facility. An additional 50 jobs will be created in other parts of the UK.