The History of Cold-Formed Steel
The use of cold-formed steel as a construction material dates back into the 1800s, although in shapes and dimensions that are quite unlike the typical framing members we see today. Corrugated iron makers started using mild steel in the 1890s, and when cold-rolled and hot-dipped galvanized it became an ideal cladding and structural sheathing for a wide range of building types for a variety of conditions and climates around the world.
A recognizable form of cold-formed steel framing appeared in the early 20th Century, most likely to mimic the dimensioned wood studs that had become the common construction method for shelter. While there are a few vague claims as to who built the first structure with CFS, an architect in Berlin…a home builder in upstate New York, an apartment complex in France … it appears that the first documented use of CFS as a building material is the Virginia Baptist Hospital built around 1925 in Lynchburg, Virginia. The walls were load bearing masonry, with a floor system framed with double back-to-back CFS lipped channels. A site observation during a recent renovation confirmed that these joists from the 'roaring twenties' are still supporting loads.
Cold-formed steel finally made a grand debut in 1933 at the Chicago Century of Progress Exposition (World’s Fair). Here, the “home of the future” exhibit area featured three homes that either made extensive use of cold-formed shapers or were completely framed with steel, including the General Houses home, the Armco-Ferro House, and the Goodhousekeeping/Stran-Steel House. CFS materials were also used as a nonstructural material in the Hall of Science. This new material was also touted in the official program of the world’s fair: “the genius of man has provided factory-made parts, wall materials pre-fabricated in shops, steel frames and clips and screws for quick assembly, and new compositions, all to permit the building of staunch structures…”
The first true foundation stone for the CFS framing industry was laid in February 1939 when the American Iron and Steel Institute’s Committee on Building Codes sponsored a research project at Cornell University that eventually resulted in the 1946 publication of the first edition of the AISI’s “Specification for the Design of Light Gage Steel Structural Members.” The release of this important document coincided with the next major event in the development in the steel framing industry: the end of World War II.
The post-war Boom
In the years immediately following World War II, a number of countries around the world faced a housing crisis. Millions of homes and commercial buildings in Japan, Germany, France and other countries had been destroyed in the global conflict. The United States and other nations faced a wave of returning soldiers who would soon be starting families and businesses.
In the US, the Lustron Corporation set out to mass-produce prefabricated homes and between 1948 and 1950 had completed 2,500 structures in 36 states and Venezuela. Unable to make a profit, however, the company eventually closed its doors. A number of other systems also came on the market during this period, including a housing development designed by architect Donald Wexler in the small community of Palm Springs, California.
CFS and the Commercial Market
While interest in steel framed homes waxed and waned, it was nonresidential construction in the US where CFS really made lasting headway as a mainstream building material. During the 1950s and 1960s, the construction of taller buildings where life-safety and constructability is a primary concern created new demand for light-weight, non-combustible CFS. New technologies also were being introduced that made steel framing construction easier and faster, including the self-drilling screw to replace “nailable” studs and wire ties for metal lath. The parallel development of tools to drive the screws during the 1950s made CFS even more attractive, and steel framing manufacturers and suppliers began to pop up across North America. During the 1960s, CFS was being used in new systems, like curtain walls, exterior framing with brick veneer, and interior shaft walls.
The initial gains in market share for cold-formed steel occurred in nonstructural applications like partition walls within the building. In 2004, the Steel Framing Alliance reported that 81 percent of interior walls built in the United States used cold-formed steel framing. With greater familiarity in the market, the establishment of building codes and standards, and availability of fire-rated assemblies, the use of structural studs also picked up steam and by 2011 had surpassed the tons used to manufacture nonstructural studs.
Today, the Steel Framing Industry Association reports that between 30 and 35 percent of all nonresidential buildings in the US are building with cold-formed steel structural and nonstructural framing.
EQ Studs
Over the past 15 years, the ability to use the properties of steel to produce more competitive products has led the development of new framing products. Perhaps the most widely adopted product is the EQ (Equivalent Gauge) studs for non-loadbearing walls.
As with the high strength steel, the EQ studs are formed from steel with higher yield strength than traditional framing studs typical in such markets as North America, Japan, and Europe. The EQ studs also take advantage of stud manufacturing methods that introduce ribs and other devices to stiffen and strengthen the flanges and webs. The higher strength steel also offers the advantage of higher pullout and shear values.
These new products are termed “Equivalent” due to the fact that the combination of the stiffening elements and higher yield strength enable the production of studs with thinner steel than traditional studs to carry the same loads. There are a number of proprietary EQ studs on the market today, accounting for 90 percent of all cold-formed steel studs used in the United States.
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Lower Costs / Higher Return on Investment
Builders, contractors and design professionals are concerned with overall system construction costs from the design phase through to the operational phase, and not simply the raw material costs of structural and nonstructural systems.
Cold-formed steel framing systems are used for cost-effective for mid-rise buildings, and are competitive with other building materials such as concrete and wood when all related construction costs are taken into consideration. The following are a few ways that cold-formed plays an essential role in lowering costs and helping maximize return on the construction investment:
Design Savings
Cold-formed steel has the highest strength-to-weight ratio of any building system, resulting in a lighter structural frame that can carry the same building loads. Lighter buildings allow the designer to reduce the mass at the foundation, cutting costs for concrete, formwork and equipment.
Quicker Installation and Erection
The predictability and accuracy of steel components speeds up the process and allows follow-on trades to get to work sooner. This delivers time savings compared to other systems. Shorter construction cycles leads to savings in site preliminaries, earlier return on investment and reduced interest charges. Time-related savings can easily amount to between 3% and 5% of the overall project value, reducing the building owner’s requirements for working capital and improving cash flow.
Lower Insurance Rates
Builders risk and property insurance premiums are typically lower for steel than wood. “Frame” or “Wood” construction has a greater likelihood to burn or be damaged by a peril (such as fire) and that the event will be a total loss versus a partial one. Loss history for wood construction has been poor and carriers are very restrictive of the amount of risk they will take (known as capacity). Total costs increase when multiple carriers are needed to provide coverage. (More detail on this subject is available by clicking this link) Insurance Savings with CFS
Increased Durability = Lower Life Cycle Costs
Steel is resilient, adaptable and durable and does not decay or age as quickly as other construction materials, which reduces life cycle costs. Cold-formed steel is protected against corrosion by a layer of zinc or similar metallic coating. A recent 10-year study conducted by the National Association of Home Builders (NAHB) Research Center found that zinc-coated steel framing systems had a predicted life that ranges from 300 to 1000 years within the building envelope, and 150 years of coating life for exterior exposures - well beyond the life expectancies of modern buildings.
Dimensional Stability and Moisture Resistance
Because steel is an inorganic material, it will not expand or contract with changes in moisture content and consequently remains dimensionally stable. Unintended structural movement with wood framing, such as warping, twisting and shrinking, can have expensive and potentially disastrous consequences on structural, mechanical, and finish systems. Additionally, with the increased emphasis on energy conservation, the long-term effects of shrinkage on the building envelope and building energy and maintenance costs must be considered.
Increased Return on Investment
The challenge for any owner/developer is to generate the maximum return for the square feet of real estate that the building sits on. Since there are no height or floor size restrictions when building with steel, building owners can maximize the number of units built on an available footprint of land, making it a much more profitable alternative than wood framing.
Conversely, code restrictions on a wood framed building’s distance/set-backs from the street and other requirements for firefighter access further limit the size of the building footprint. This results in less usable space for the occupant and along with it the revenue the building owner can generate.
No Hidden Site Construction Cost
When building with steel, owners can take comfort in the fact that there are no hidden or extraordinary site construction costs involved, unlike the growing list of site fire safety requirements for combustible framing systems. These requirements include the need to submit a detailed fire safety plan during the permit approval stage, install sprinklers as each floor is built, increase supervision during hot work, a general increase in site supervision and a significant increase in site security. Several jurisdictions are requiring builders to post 24-hour security guards at wood- frame construction sites. One builder has reported additional costs of $6,000 to $10,000 per month while construction is underway, and another reported that the additional security added $20,000 to an $8 million project.
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Durability that Lasts a Lifetime
Long life is a primary attribute necessary for all building materials and a key component of resilience, but is especially important for structural materials and finishes in areas where moisture from atmospheric conditions or inadvertent exposure to moisture occurs. Even though all materials need to be protected through effective claddings and barriers, it is reasonable to assume some breakdown of those protections will occur. Plumbing or roof leaks are also unplanned but do occur. Similarly, a breakdown in the building envelope creates opportunities for pests like termites and carpenter ants to attack a structure. Consequently, choosing materials that won’t sustain significant damage from moisture or pests is an essential.
Corrosion resistance. Cold-formed steel has a resistant coating that effectively protects steel from corrosion. This coating must meet the requirements of ASTM A1003 “Standard Specification for Steel Sheet, Carbon, Metallic- and Nonmetallic-Coated for Cold-Formed Framing Members.” The recognized test standard for measuring corrosion resistance is ASTM B117 “Standard Practice for Operating Salt Spray (Fog) Apparatus.” Compliance to these standards is assured through the Steel Framing Industry Association Code Compliance Program. This is a mandated program that all SFIA members must meet.
With the proper coating and construction techniques, the protective barrier over cold-formed steel will last nearly 700 years, even under extreme conditions such as near aggressive salt-laden waters. Unlike other structural materials, steel can be ordered with extra heavy zinc or similar coatings for even more durability. New types of metallic coatings have also been recently introduced, referred to as EQ (equivalent) coatings, and used to supplement the layer of zinc to achieve higher corrosion resistance performance.
Another critical characteristic for building materials in moisture mitigation is water retainage. Some materials absorb water in a flood situation and exacerbate the situation. It is important after a flood that the space is dried out as quickly as possible. The EPA has stated there is a window of 24-48 hours to effectively reduce the potential for mold propagation. That time window can be severely taxed if the building materials in the space absorb and hold moisture. Steel does not retain water.
 Termites. Approximately five billion dollars of damage occur each year due to termite infestations in the United States and represent a significant threat to the long-term resilience of a building throughout most of the US and particularly in warmer climates.
Cold-formed steel is one of the few materials that can resist termites in nearly any climate or building type. Even though it seems like termite damage would be a long-term issue, when a hurricane or other high winds strike, it pays to have a building that performs as designed, versus one that may be weakened by termite damage.
The Formosan termite poses a unique threat to buildings across the southeast and gulf coast regions in the United States, as well as in Hawaii and other tropical locations. Unlike the more traditional subterranean termite that attacks from the ground up, the Formosan termite can establish colonies even on the roof due to its ability to attack aerially. In these areas, using cold-formed steel framing for the entire structure will increase the building’s resilience.
 Mold. Preventing exposure to susceptible materials during a flood or even under normal conditions in some areas is critical to preventing mold, mildew, and structural deterioration.
Although the safest approach may be to elevate a building above the flood elevation, that is not always practical or even possible in some areas. When it is a reasonable approach, extra protection can be added by using another foot or two of “freeboard” above the flood elevation.
 An alternative approach is to not use susceptible materials in flood-prone areas in the first place. Cold-formed steel is inherently a good choice for any framing where it may get wet during a flood. Unlike wood framing, cold-formed steel is inorganic and won’t provide a source for mold and mildew. Even in extreme coastal environments, the long term life of cold-formed steel framing used in accordance with AISI design standards and U.S. building codes has been shown to be hundreds of years, or well beyond the expected life of a building.
The use of cold-formed steel framing can mitigate two of those concerns. Since steel will not absorb water like, it will not retain dampness in the space. In effect, steel framing will aid in drying out the space faster for it won’t serve as a moisture reservoir.
When floods and leaks do occur, organic materials represent the perfect materials for mold growth. Non-organic materials such as steel don’t support mold growth.
Steel is inorganic. It will not function as a food source for mold. Further, steel is dimensionally stable in a moist environment. It will not warp. Walls and floors remain plumb and level in a wet environment. |
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Sustainable Steel
 Recycling. The Steel Recycling Institute (SRI) reports that steel is recycled more than paper, plastic, glass, copper, lead and aluminum combined. All steel products, including steel framing, contain recycled steel. Steel framing contains on average a minimum of 25% recycled steel and is 100% recyclable at end of life. Using recycled steel takes the pressure off renewable resources: about six scrapped cars are needed to build a typical 2,000-square foot home with steel framing. Finally, in contrast to many other building materials, steel is routinely collected in aggregate quantities from construction and demolition sites and recycled into new steel products.
Courtesy: American Iron and Steel Institute
 Energy and Emissions. Since 1990, the US steel industry has reduced energy intensity by 32% and CO2 by 37% per ton of steel. Globally, the World Steel Association states that world-wide, the steel industry has reduced energy consumption since the 1970’s in the manufacture of steel by 50%. This directly relates to a reduction in greenhouse gas emissions.
A Sound Environment. In terms of acoustics, the use of cold-formed steel framing is instrumental in achieving acoustical privacy. Acoustical privacy from one room to the next is a function of the Sound Transmission Classification, STC, of the separating assembly. This assembly can either be a wall or a floor-ceiling assembly. STC is a single number rating system that gives a comparative look at how well an assembly impedes sound energy as it moves through the assembly. Essentially the higher the STC, the greater the acoustical privacy. Cold-formed steel framed assemblies have been tested and achieved STC’s in the mid-60’s, well above the mandatory minimums in the International Building Code.
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