Root gap refers to the distance between the two pieces of a groove weld at the bottom of a joint.

Root gap refers to the distance between the two pieces of a groove weld at the bottom of a joint.

• A. The distance between edge of base metals at root
• B. The distance between the two pieces of a groove weld at the bottom of a joint
• C. The width of the weld toe
• D. The distance between fillet welds

Answer: (B)

Root gap is the space between the two pieces of base metal at the root of a groove weld, the open distance at the bottom of the joint where fusion occurs. This gap matters because it controls how easily the weld can fuse properly at the root and how much filler metal is needed for complete joint penetration. If the gap is too large, achieving full root fusion becomes difficult and you may end up with underfill or excessive welding heat. If it’s too small, you risk incomplete fusion or burn-through at the root. The other terms describe different features: the width of the weld toe is where the weld meets the base metal along the edge, and the distance between fillet welds is irrelevant to groove weld joints.

Root gap is the space between the two pieces of base metal at the root of a groove weld, the open distance at the bottom of the joint where fusion occurs. This gap matters because it controls how easily the weld can fuse properly at the root and how much filler metal is needed for complete joint penetration. If the gap is too large, achieving full root fusion becomes difficult and you may end up with underfill or excessive welding heat. If it’s too small, you risk incomplete fusion or burn-through at the root. The other terms describe different features: the width of the weld toe is where the weld meets the base metal along the edge, and the distance between fillet welds is irrelevant to groove weld joints.