Structural engineers and architects have been improving the buildings that we live, work and socialize in, since the beginning of man. Not only has the design of these structures improved, but the materials have vastly changed. This week I look into one material that, while not uncommon, has seen a major increase in use. Light gauge galvanized steel studs have been used in commercial construction for decades, however due to rising lumber costs and the desire to preserve lumber; use in residential construction has become increasingly common. According to the National Association of Home Builders, shipments of light gauge steel for residential building grew by almost 44 percent in 1998
[i]. While many do not see any negatives to using metal, there are drawbacks to using this non-traditional residential building material.
Along with the notable fact that steel is stronger than wood in many ways, the environmental and thermal properties are some other positives for the selection of this material. Impervious to most elemental causes, steel studs do not warp, rot, shrink, crack, or split like traditional wood studs can. Steel is also not effected by termites or other insects that can destroy or contribute to costly repairs to a structure. Natural disasters, such as tornadoes and earthquakes, do not effect steel studs the same as wood. This fact has led homebuilders in tornado prevalent areas to make the switch to steel more quickly. The Steel Framing Alliance (SFA) reported that while only 7 percent of homes in Florida have steel studs, 47 percent of homes in South Florida have them[ii]. The most notable upside for using steel, and why it is so widely used in commercial buildings, is the fire resistant abilities. While steel will be weakened by fire, it will not burn like it’s wood counterpart. The melting point for steel is between 11000C and 16500C. It is this high melting point that allows for a steel structure to withstand a fire longer before collapsing.
Finding quality wood for studs is another issue avoided when using steel. Lumber, used for studs, has to be straight and cannot have any imperfections such as knots or cracks. During the building process, approximately 20 percent of lumber purchased is wasted due to imperfections, compared to approximately 2 percent when using steel[iii]. Both materials, are however, able to be easily recycled and used in other forms. While there are variations of wood and varying levels of quality, the steel industry sets standards that all studs must meet, ensuring the uniformity of the building product. When a uniform and sturdy product is necessary, steel looks like the way to go.
While it would seem that steel is the ideal product for studs, there are still drawbacks to the product. The composition makeup of the steel when secured does not have the same flexibility as wood and is therefore sometimes not as workable. Studding door frames is one instance where you would likely see wood and steel working together. Due to metal’s electrical conductivity, different cables and electrical boxes are required during construction and this can be an added cost. While steel can be recycled and reused, the process necessary to melt the metal and reform it does produce pollutants. Do the benefits received from recycling steel out weigh the added air pollution? Being that steel is less energy efficient than wood, special insulation made of extruded polystyrene is required and placed primarily inside of the exterior walls to assist with the thermal management of the structure. Also, special moisture-proof barriers are installed in environmental areas that get both cold temperatures and high levels of humidity. This along with the zinc coating (galvanized) prevents the steel from rusting. Noise is another downside to utilizing steel studs as they tend to reflect sound vibrations rather than absorb. Placement of back to back studs, or double studding, is used on interior walls to help reduce noise transmission.
While steel is a strong alternative to wood in terms of strength and installation ease, do the required modifications and material additions necessary to use steel really make it a superior product? This is one of those questions that does not have a right or wrong answer. There are benefits and downsides in most aspects, from cost to installation as well as environmental and thermal or energy factors.
With the world population on the rise and the continued need for new, stronger and safer construction, steel studs may become the norm in residential construction. While special insulation, wiring, and moisture barriers are required, steel studs are extremely beneficial and cost efficient in the long term.