Metal studs are made of thin steel sheet that has been cold-formed into a C-shape or U-shape and coated with zinc to resist corrosion. The steel itself is a low-carbon variety, and the zinc coating (called galvanization) is what gives metal studs their signature silver appearance and long-lasting durability. Beyond that simple answer, the specific grade of steel, the thickness of the zinc layer, and the manufacturing process all vary depending on whether the stud is meant to carry structural loads or simply frame an interior wall.
Steel Sheet: The Core Material
The base material in every metal stud is steel sheet, manufactured to standards set by ASTM International. Two specifications dominate the industry: ASTM A1003 and ASTM A653. Both describe steel that is strong enough to frame walls, floors, and ceilings while remaining thin enough to be shaped at room temperature without cracking.
Steel studs come in different strength grades measured by yield strength, which is the amount of force the steel can handle before it permanently bends. The two most common ratings are 33 ksi and 50 ksi (ksi stands for “thousand pounds per square inch”). Grade 33 steel, with a yield strength of 33,000 psi, is the standard choice for non-structural partitions like interior office walls that don’t bear any weight from above. Grade 50 steel, rated at 50,000 psi, is used for structural framing, including load-bearing walls, floor joists, and exterior wall systems where the stud must resist wind loads and support the structure above it.
Thicker studs tend to be specified at the higher grade. Industry guidelines call for Grade 50 steel in studs that are 54 mils (about 1.37 mm) thick or heavier, while studs 43 mils (about 1.09 mm) thick or lighter typically use Grade 33. The “mil” measurement refers to the thickness of the bare steel before any coating is applied, and it directly affects how much load a stud can carry.
How Cold-Forming Works
Metal studs get their shape through a process called cold-forming, which means the steel sheet is bent and rolled into its final profile at room temperature rather than being heated first. Large coils of flat steel sheet are fed through a series of rollers that progressively bend the material into a C-shape (for studs) or a U-shape (for tracks, which are the top and bottom channels that studs slide into).
The C-shaped studs have stiffened flanges, meaning the lip at the edge of each flange is folded inward to add rigidity. Tracks, by contrast, have straight, open flanges so studs can be inserted into them. Most studs also come with pre-punched holes in the web (the flat center section) to allow electrical wiring and plumbing to pass through without on-site drilling.
Cold-forming doesn’t change the chemical makeup of the steel, but it does slightly increase the material’s hardness along the bend lines. The entire process is governed by AISI S100, the North American standard for designing cold-formed steel structural members, which ensures that every stud performs predictably under load.
Zinc Coating for Corrosion Protection
Raw steel rusts quickly when exposed to moisture, so every metal stud is coated with a layer of zinc through a process called hot-dip galvanization. The steel sheet is dipped in molten zinc before it is cold-formed, creating a metallic bond between the zinc and the steel surface. This is what makes metal studs corrosion-resistant and suitable for decades of service inside walls.
Zinc does more than just act as a barrier. It provides what engineers call sacrificial protection: if the coating gets scratched or nicked during installation, the surrounding zinc will oxidize slightly faster and fill the scratch with zinc oxidation products, preventing the underlying steel from rusting. This self-healing behavior is one reason galvanized steel studs hold up so well over time.
The thickness of the zinc layer is described by a “G” designation, and the number corresponds to the total weight of zinc on both sides of the steel in ounces per square foot:
- G40 is the standard coating for non-structural framing, like interior partition walls in offices and homes.
- G60 is the standard for structural framing. A G60 coating means 0.60 ounces of zinc per square foot total, which works out to roughly 0.5 mil (half a thousandth of an inch) of zinc on each side.
- G90 offers a zinc layer that is 50 percent thicker than G60. Because corrosion resistance is directly proportional to zinc thickness, G90-coated studs last roughly 1.5 times longer than G60 studs. Several manufacturers market G90 framing specifically for coastal areas, humid climates, or any application where moisture exposure is a concern.
Recycled Steel Content
All cold-formed steel framing contains a minimum of 25 percent recycled steel, according to the Steel Stud Manufacturers Association. This recycled content comes from a mix of post-consumer scrap (old cars, appliances, demolished buildings) and pre-consumer scrap generated during the steelmaking process. Steel is one of the most recycled materials on the planet, and because electric arc furnaces can melt scrap into new steel coils efficiently, that recycled percentage is a baseline, not a ceiling. Many steel coils used for stud production exceed the 25 percent minimum.
Product Markings and What They Tell You
Every metal stud is stamped on its web with identification markings spaced no more than four feet apart. These markings are there so inspectors, contractors, and architects can verify the stud matches what was specified. A typical stamp includes the manufacturer’s name, the minimum uncoated steel thickness in mils, the zinc coating designation (G40, G60, or G90), the minimum yield strength, and an ICC evaluation report number that ties the product back to its tested performance data.
If you pick up a metal stud at a supply house and see something like “54 mil / G60 / 50 ksi” stamped on the web, that tells you the stud is 54 mils of bare steel, coated with a G60 zinc layer, and rated for a yield strength of 50,000 psi. That combination would be a structural stud suitable for load-bearing walls.
Structural vs. Non-Structural Studs
The composition of a metal stud shifts depending on its intended role. Non-structural studs, sometimes called drywall or partition studs, use thinner steel (often 18 to 33 mils), a lighter G40 zinc coating, and Grade 33 yield strength. They are designed to hold drywall and support their own weight, nothing more. You will find these in interior walls that divide rooms but don’t carry loads from above.
Structural studs are heavier gauge, typically 33 to 97 mils thick, with G60 or G90 zinc and Grade 50 steel. They replace wood 2x4s and 2x6s in load-bearing walls, headers, and floor systems. The higher yield strength and thicker zinc make them suitable for exterior walls exposed to weather, multi-story buildings, and any application where the framing must transfer roof, floor, or wind loads down to the foundation.
Both types start from the same basic recipe of steel and zinc. The difference is simply how much of each is used, which determines how strong and how durable the finished stud will be.