The exterior wall carries the second floor and the roof, and the studs installed in it are marked with an uncoated base steel thickness of 18 mils. What is the correct finding?
- AAcceptable, because 18-mil members are the standard thickness for cold-formed steel wall framing whether the wall carries load or not
Cold-formed steel comes in two families, and 18 mils belongs to the nonstructural one made for interior partitions. Treating it as the standard puts a partition stud under a floor and a roof.
- BAcceptable, because it is the coating thickness rather than the uncoated base steel thickness that governs the structural capacity of a steel wall stud
The stamp reports uncoated base steel thickness because that is what carries load, while the coating is corrosion protection. Reading the wrong figure turns an 18-mil member into an apparently adequate one.
- A violation, because 18-mil members are nonstructural material and a load-bearing wall requires at least the minimum structural thickness of 33 mils
- DA violation, because interior partitions and exterior bearing walls have to be framed from the same thickness of cold-formed steel members
Nothing requires partitions and bearing walls to match, and nonstructural members are the right product for a partition. The failure is using them in a wall that carries a floor and a roof.
Why C is correct
The 33-mil threshold is the dividing line between nonstructural and load-bearing cold-formed steel. An 18-mil member is drywall framing; it has no published capacity for carrying a floor and roof, so the inspector rejects it on identification alone without needing to run any numbers.
What this question is testing
Whether the candidate can distinguish structural from nonstructural cold-formed steel by base thickness, and understands the difference between coating designation and base steel thickness. It further tests whether the candidate can reject material on identification alone, without needing a calculation, and knows to check more than a single stud before clearing the wall.
On the job
This happens when a drywall subcontractor is asked to frame a few interior walls and their material ends up in an exterior bay, or when a supplier fills a shortfall from the nonstructural rack. It is invisible until someone reads the embossment. The consequence is real, since an 18-mil stud under floor load will buckle. Inspectors on steel-framed jobs read markings in several bays per wall rather than trusting a single sample.
Memory technique
Thirty-three to carry, eighteen just to divide.
Exam tip
Remember 33 mils as the floor for load-bearing steel studs; anything thinner belongs in a partition.
Where to look it up
IRC Chapter 6 cold-formed steel wall framing, the material and minimum thickness provisions.