Cold-Formed Steel (CFS) is the common term for products made by rolling or pressing thin gauges of sheet steel into goods. Cold-formed steel goods are created by the working of sheet steel using stamping, rolling, or presses to deform the sheet into a usable product. Cold worked steel products are commonly used in all areas of manufacturing of durable goods like appliances or automobiles but the phrase cold form steel is most prevalently used to described construction materials. The use of cold-formed steel construction materials has become more and more popular since its initial introduction of codified standards in 1946. In the construction industry both structural and non-structural elements are created from thin gauges of sheet steel. These building materials encompass columns, beams, joists, studs, floor decking, built-up sections and other components. Cold-formed steel construction materials differ from other steel construction materials known as hot-rolled steel. The manufacturing of cold-formed steel products occurs at room temperature using rolling or pressing. The strength of elements used for design is usually governed by buckling. The construction practices are more similar to timber framing using screws to assemble stud frames.
Cold-Formed Steel Framing
Cold-formed steel framing (CFSF) refers specifically to members in light-frame building construction that are made entirely of sheet steel, formed to various shapes at ambient temperatures. The most common shape for CFSF members is a lipped channel, although “Z”, “C”, tubular, “hat” and other shapes and variations have been used. The building elements that are most often framed with cold-formed steel are floors, roofs, and walls, although other building elements and both structural and decorative assemblies may be steel framed.
Although cold-formed steel is used for several products in building construction, framing products are different in that they are typically used for wall studs, floor joists, rafters, and truss members. Examples of Cold-Formed Steel that would not be considered framing includes metal roofing, roof and floor deck, composite deck, metal siding, and purlins and girts on metal buildings.
Framing members are typically spaced at 16 or 24 inches on center, with spacing variations lower and higher depending upon the loads and coverings. Wall members are typically vertical lipped channel “stud” members, which fit into unlipped channel “track” sections at the top and bottom. Similar configurations are used for both floor joist and rafter assemblies, but in a horizontal application for floors, and a horizontal or sloped application for roof framing. Additional elements of the framing system include fasteners and connectors, braces and bracing, clips and connectors.
In North America, member types have been divided into five major categories, and product nomenclature is based on those categories.
- S members are lipped channels, most often used for wall studs, floor joists, and ceiling or roof rafters.
- T members are unlipped channels, which are used for top and bottom plates (tracks) in walls, and rim joists in floor systems. Tracks also form the heads and sills of windows, and typically cap the top and bottom of boxed- or back-to-back headers.
- U members are unlipped channels that have a smaller depth than tracks, but are used to brace members, as well as for ceiling support systems.
- F members are “furring” or “hat” channels, typically used horizontally on walls or ceilings.
- L members are angles, which in some cases can be used for headers across openings, to distribute loads to the adjacent jamb studs.
In high-rise commercial and multi-family residential construction, CFSF is typically used for interior partitions and support of exterior walls and cladding. In many mid-rise and low-rise applications, the entire structural system can be framed with CFSF.
Steel is one of the most sustainable building materials in the world. The industry has embraced the common sense approach that reducing its impact on the environment is not only the right thing to do, but it makes economic sense.
- Since the early 1990s, the steel industry has reduced its energy use to produce a ton of steel by approximately 1/3.
- More than 95% of the water used in the steel making process is recycled and returned – often cleaner than when it was taken from the source.
- Every piece of steel used in construction contains recycled content. Further, all steel can be recovered and recycled again and again into new high quality products.
- Steel is durable, safe, and strong. It is not susceptible to rot, termites, or mold. Steel used for framing will last from hundreds to over a thousand years due to its zinc coating, a natural element. Steel structures require less material (both reduced weight and reduced volume) to carry the same loads as concrete or masonry or wood structures.
- Steel is dimensionally stable: it will not warp, split, or creep – making it durable and built to last. Don’t waste time and dollars on costly call backs. Minimize cracking and pops in drywall and other finishes with CFS framing.
Steel and Green Building Codes and Standards
As more and more green codes and standards begin to make their way into adoption, cold-formed steel (CFS) is well positioned to help your project meet the highest sustainability standards. Steel is recognized in all major green building standards and rating programs, including the National Green Building Standard (ICC-700) for residential buildings, ASHRAE Standard 189.1 for commercial construction, and the US Green Building Council’s LEED program that covers all types of buildings. How is this possible? More than 82 million tons of steel were recycled in the US in 2008 – more than aluminum, glass and paper combined. That steel goes back into new studs, joists, and other members used in buildings. In fact, steel is the only material with an automatic minimum default value for recycled content in the LEED program. Further, most green codes and standards recognize the excellent potential of CFS at reducing the amount of construction waste generated at a site. Most of this is due to the almost universal use of pre-engineered and assembled panels to build steel assemblies using modern, efficient technology. For example, of all the waste from a 2000 sq. ft. residence framed with steel, less than 2 % of steel is left over and can be recycled compared to that same house built of wood generating 20% of waste that will be sent to landfill.
Additional Information & Original Link:
Lt. John Shafer