6 4 mm or more.
How to seam copper sheets.
It is arguably the most time proven type of roof panel seam.
This video describes how to make a double lock standing seam with a seaming anvil and a hammer.
Fabricate nonmoving seams in copper sheet with flat lock seams.
This type of seam is used wherever significant movement of the copper sheets is expected.
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The backhand method is preferred for thicknesses of 1 4 in.
Where lapped or bayonet type expansion provisions in work cannot be used or would not be sufficiently water weatherproof form expansion joints of intermeshing hooked flanges not less than 1.
Tin edges and cleats to be soldered form seams and solder.
For sheets up to 1 8 in.
When welding thin sheets the forehand welding method is preferred.