adding to existing fillet weld

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I have a condition where a 1/4" fillet weld has already been made.  Now, a 5/16" fillet weld is required.  Is it acceptable to just ad the additional 1/16" of weld?  Or, do I need to burn of the existing weld and provide a new 5/16" weld?Thanks!
Reply:Unless you are prohibitedd from making multipass fillet welds, adding metal is fine. I would suggest reviewing the project specifications to see if there is anything that prohibits this. Adding weld may make the weld too large (Adding 1/16" could be tough with some processes)Many codes, industry standards and project specifications exists that may very well prohibit this.For instance,  AWS D1.1 says 5.26.1.2 Excessive Concavity of Weld or Crater,Undersize Welds, Undercutting. The surfaces shall beprepared (see 5.30) and additional weld metal deposited.\The preparation is 5.30.1 In-Process Cleaning. Before welding over previouslydeposited metal, all slag shall be removed and theweld and adjacent base metal shall be cleaned by brushingor other suitable means. This requirement shall applynot only to successive layers but also to successive beadsand to the crater area when welding is resumed after anyinterruption.Have a nice dayhttp://www.weldingdata.com/
Reply:Personally I would grind or gouge it out depending on length.  Then reweld to 5/16".  That's going to look the best.  Making a 1/4" fillet into a 5/16" fillet and making it look nice will be difficult.  If a 3/8" fillet is acceptable, then adding two more passes to make a 3 pass 3/8" fillet might yield ok appearance.  Building up using tig would get you to 5/16" without much problem, but then you've got one weld with a difference appearance than the rest of the part, assuming the whole thing wasn't tigged in the first place.
Reply:Gaustin gave good advice.  If it's TIG, it would be easy to put just 1/16" more on top of what you have.  You likely will be fine if the weld is a little too big.