Canadian Welding Bureau Level I Practice Exam 2026 – Complete Exam Prep

Backing welds are placed to support and define the root of a groove weld. They are added during the initial weld stage, before the groove weld is completed, so the root bead has something to fuse to and so proper penetration and weld geometry are established from the start. If you wait until the groove weld is finished, the root may not fuse properly and you lose the backing support, which can lead to lack of penetration or defects. The timing described ensures a solid root and a stable base for the remaining weld passes.