Corrosion Resistance

  • Properly designed and constructed steel structures provide long-term durability.
  • Laboratory and field exposure tests on steel structures built to industry standard practices demonstrate excellent service life.
  • Building codes and industry standards require that steel structures be designed to tolerate corrosion or be protected against corrosion where corrosion may impair strength or serviceability.
  • Barrier coatings (such as paint) are readily available to coat the steel surface and isolate it from water and oxygen. Without water and oxygen, the steel cannot corrode.
  • When further protection is needed, zinc coatings (such as galvanized) are available to provide sacrificial protection as well as barrier protection. When the base metal of a zinc-coated steel is exposed, such as at a cut or scratch, the steel is cathodically protected by the sacrificial corrosion of the zinc coating adjacent to the steel.
  • When there are severe exposure conditions, such as industrial atmospheres and marine atmospheres, higher-performance coatings are available.
  • For fabricated structural steel, HSS and open web steel joists, a variety of shop and field-applied paint and zinc coatings are available.
  • For sheet steel, a variety of hot-dip galvanized coatings applied by the steel mill and/or paint coatings applied by a coil coating line are economical and readily available. These coatings are applied to the sheet steel prior to the coil being shipped to the manufacturer for roll forming of the finished product.
  • Zinc-coated steel, which is standard for cold-formed steel framing, will last far beyond the life of a building when properly installed and insulated, and is especially appropriate in the high-demand structural configurations of mid-rise construction.
  • Industry guidance is readily available from the steel construction associations. Following are some suggested resources:

Mold Resistance

  • Steel framing is resistant to mold since it is inorganic and does not provide a food source for mold to grow.
  • Steel framing can help resist the onset and growth of mold since its framing members are dimensionally straight and connected mechanically (screwed vs. nailed), offering a tight envelope with no nail pops or drywall cracks (e.g., where the roof meets the walls). This makes the building structure stronger and more resilient.
  • Ventilation is efficiently built into a steel-framed design, and energy efficiency is maintained or increased due to steel's inorganic properties.
  • Moisture does not get into steel studs, substantially eliminating the expansion and contraction of construction materials around windows and doors, where leaks can occur.

Vermin Resistance

  • Termites cause more damage to structures than fire, floods, and storms combined. Of particular concern is the Formosan termite, one of the most destructive termite species in the world. Originally limited to Hawaii, it is now well established throughout the southern United States around the Gulf Coast and spreading rapidly.
  • Steel framing is not vulnerable to termites since it is inorganic and does not provide a food source for them.
  • Cold-formed steel is one of the recognized methods for compliance with the termite-resistant construction requirements of the International Residential Code.
  • There is no need for annual termite treatments with steel.
  • Cold-formed steel provides a healthy building with no off-gassing from chemical termite treatments or pressure-treated lumber.
  • Termite damage is rarely covered by insurance. Building with steel allows owners to avoid costly problems later.

Dimensional Stability

  • When considering framing systems, particularly for mid-rise structures, the dimensional stability of the framing materials must be given careful consideration before and during the design and construction process.
  • Unintended structural movement can have expensive and potentially disastrous consequences on structural, mechanical, and finish systems.
  • When using materials that shrink or swell with changes in moisture content and changes in relative humidity, it is important to consider a variety of implications whether the material is the only framing material employed or is used in combination with steel or other materials that do not exhibit the same changes in the presence of moisture.
  • Dimensional stability concerns are magnified when materials are used in a mid-rise building. Although a material might be used successfully in low-rise buildings, the same construction practices cannot be assumed to be adequate for taller structures.
  • The best way to avoid dimensional stability problems is to build with a dimensionally-stable material such as steel.
  • Steel structures provide long-term, consistent performance.
  • Steel does not expand or contract with moisture content.
  • Steel does not warp, split, crack or creep.
  • Steel is isotropic, meaning it has the same dimensional properties in all directions.  Since there is no "grain," the strength of steel is the same up and down, side-to-side, and in all loading directions.
  • When they get wet, both wood and brick will swell.  When they dry out and cure, concrete and concrete block will shrink and form shrinkage cracks.
  • Using steel not only solves issues with structural movement due to changes in moisture content or humidity, but eliminates or greatly reduces other moisture related issues such as rot and mold.
  • Wood is particularly prone to dimensional instability.
    • If wood is considered for the primary framing material, or even for components of the structure such as exposed wood beams or timber frame trusses, the shrinkage of the wood and the associated cost of the special detailing required must be considered.
    • In addition, with the increased emphasis on energy conservation, the long-term effects of shrinkage on the building envelope and building energy and maintenance costs must also be considered.
    • The cost of repairing cracks in framing and finishes, as well as painting, caulking, sealing, and termite protection should all be considered.

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