Reading a Steel Stud Stamp

Gauge is the old system and it is imprecise — a "20-gauge" stud from two makers could be different thicknesses. The industry moved to mils, thousandths of an inch. The stamp says mils. The common ones: 18 mil is what used to be 25 gauge. 30 mil is 20 gauge. 33 mil is 20-gauge structural. 43 mil is 18 gauge. 54 mil is 16 gauge. 68 mil is 14 gauge.

The stamp also says the minimum yield — 33 ksi or 50 ksi. Two studs of the same thickness with different yields carry different loads, and the engineer's schedule specifies both. A 43-mil 33-ksi stud is not a substitute for a 43-mil 50-ksi one, and the inspector can read the stamp as well as you can.

Equivalent. A 20-gauge EQ stud is thinner steel — often 18 or 19 mil — with a higher yield and a stiffened profile, engineered to perform like a conventional 30-mil stud in a non-load-bearing wall. It is lighter and cheaper and it is what the trade uses for partitions. It is not a structural stud, and the stamp will not say it is.

Every stud has a limiting-height table — how tall a wall it can frame at a given spacing and deflection limit. ClarkDietrich and CEMCO both publish them. Text us the wall height and spacing and we will read it for you; it takes a minute and it is the difference between a wall that passes and one that flexes.