Sheet Metal & Air Conditioning Contractors’ National Association

Papers and Guidelines


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Soldering Copper Flat Lock Roof Seams

The International Training Institute (ITI) commissioned Simpson Gumpertz & Heger Inc. (SGH) to evaluate 1/2 inch wide flat lock seam soldered joints. The industry’s current recommended widths are 5/8 inch wide flat lock seams (Architectural Sheet Metal Manual by SMACNA) and 3/4 inch wide flat lock seams (Copper and Common Sense by Revere Copper).

The study investigated the in-service cyclical thermal loads that flat seams typically experience, and to test varying levels of dressing extent, joint gaps, voids in solder, edge seam solder geometry, and solder extent, to help analyze the minimum requirements for meeting the intended service life of 75 years without failure in a 1/2 inch wide flat lock seam.