Post date: Jun 21, 2015 6:43:52 AM
I was reading the architect's specification for the sheet metal used to line the canales (scuppers) where he calls for “26 ounce” copper. Oh? I have seen fabric and paper graded by density (weight per unit area), but never sheet metal. Here are two size descriptions from Basic Copper:
Ach, du lieber! I find from Storm Copper that for roofing applications, “To make matters even more confusing, the roofing industry measures copper thickness in ounces per square foot. 16 oz. copper sheet is a very common size of roofing copper. Listed below are product links that cross reference inches to gauge.” However they don’t cross-reference density vs. thickness.
Alaskan Copper and Brass does have a density vs. thickness vs. Birmingham Wire Gauge (BWG) chart, but 26 ounce seems not to be shown:
I do wish the Americans had switched to the metric system a few decades ago.
The Copper Development Association gives a table:
It looks as though that industry has a ‘nominal’ measure but actually delivers much less (‘minimum’).
Again, there is no ’26 ounce’ material. It seems that 24 and 26 gauge are used for roofing.
It turns out that the same number gauge means very different thickness, depending upon which metal you are measuring. “US Standard”, Galvanized Steel, Stainless Steel, Aluminum, Copper, and Zinc all use variants of the same set of number gauges, as explained by Riverside Sheet Metal.
This is about as rational as many of the other things our legislators do.