am struggling with the difinition of a concave weld and what is acceptable. Can you have a SAW weld with a reinforcement height not in excess of 1/8 inch and have the center of the weld dip down as long as it doesn't go below the base metal? I am using AWS D1.1 2004 and looking at Figure 5.4 which lists underfill but no mention of concavity in a butt weld. Under 5.26.1.2 Repairs it has Excessive concavity which leads me to believe that some concavity is acceptable.