Wood is a natural resource that used to be used in abundance for the construction of Houses. However, with the diminishing supply of wood owing to depletion of wood reserves, alternate materials are being looked into for the construction of houses. Over the past decade overall lumber prices have both increased and become more volatile. Surprisingly two of the most admired modern houses are made of steel. One by Philip Johnson known as Glass House and the second by Meis van der Rohe known as Farnsworth House. In spite of these excellent landmarks built in the first half of the 19th century, we are just now on the threshold of steel construction for house design.
Steel may not have caught the eye up until now owing to the fact that the tooling required for steel home production is more exacting than that for wood or masonry, and the market was limited. Manufacturers typically don’t do one-off designs, preferring to do multiple units to achieve economies of scale. This is the main cause for not accepting steel as the main building material used by architects. It limits the designs. But housing as a dwelling is not guided by design, but instead it is the durability and the cost effectiveness of the building that is of paramount concern for an average person who wants to build a house.
In 1991, for the market in the United States, lumber costs for a 2,000 square foot home averaged about $5,000. In 1993, the lumber cost for the same size home was about $12,200 (up to $491 per 1,000 board feet). As the framing costs are accounting for almost 20 percent of the total cost of the home, and a homebuilder always tries to strive for maximum benefits from optimum costs, alternate products are always being looked into. (Warte, 2000) Alternate products are also given a trial when they have a pricing that is competitive to traditionally used materials.
In 1993, for the first time in the United States, the price of a steel-framing package started to become competitive with a wood package for the same components used in house building. Thatâ€™s when builders began thinking about switching from wood to steel framing. This alternative of steel was also being looked into as the quality of wood available was deteriorating owing to cutting before the required tempering which was not providing the desired tensile strength.
The first usage of steel frames was in wall frames. Steel joists and trusses can achieve greater spans, opening up large spaces inside a home. It provided additional space for the architects to play with inside the house. Steel as a medium had the advantage in that it is able to have both tensile stress and also the comprehensive stress in the same magnitude, which is not the case with either wood or reinforced concrete. From being used in 27170 walls in USA in 1997, the number of walls usage had jumped to 51554 in 2002 ( Fanjoy, 2003)
Advantages of Steel Framing
Characterized by high quality, steel houses are made from uniform quality material, its walls are straight, with square corners, and eliminates to a large extent pops in dry walls, which one has to bear with in the case of either wood or RCC walls (Loree,2003 ). Apart from saving precious wood for construction, walls of steel are non-combustible and hence are fire resistant, and they cannot be infested with termites, as steel is inorganic. Being fire resistant means that the insurance premium for such houses is much less, as compared to that for a normal house. (Scharff, 2003).
In Hawaii in 1998, over one-third of all new homes were built with steel to protect against the voracious Formosan termite. Its allowable stress values on average range from 21,000 to 33,000 pounds per square inch (psi). Specific advantages offered by the use of steel framing in a seismic event include the following considerations:
Steel is a stable material with consistent chemical attributes. Once the steel stud has been formed, it will remain straight with virtually no change to the thickness, width or other dimensional properties.
Because the material and geometric properties of a steel-framing member are stable, the overall strength of the structure will depend upon the quality of connections between the studs
Used with adequate insulations, steel-framed homes can be as energy efficient as wood-framed homes. All light gauge steel framing contains a minimum of 25% recycled steel. The major environmental benefits of steel framing include:
a. A 25% minimum recycled content and 100% recyclability;
b. Minimal job site waste due to standard quality (2% for steel vs. 20% for wood);
c. Life cycle energy savings due to the air tightness of the structure
d. A long structure life reducing the need for future building resources (zero depletion of iron resources).
The use of steel-framed members enables builders and designers to earn credit points under Leadership in Energy and Environmental Design (LEED) Programs. The recycled content value of the steel produced exceeds the 5% and 10% goals in LEED (Warte, 2000).
It cannot be seen by the naked eye that a house has been built using a steel frame, as steel framed homes can be finished with the same materials (interior and exterior) used to finish wooden homes.
It also facilitates faster paneling and facilitates in speeding up the on site construction process by allowing the assembly of walls in controlled environments. Steel framing members also have pre-punched holes that allow for easy installation of electrical wiring and plumbing. The variety of sizes and thickness of steel contribute to flexibility. Being lightweight, it is easy to handle, so it facilitates in reduced labor costs and worker fatigue, and cold-formed steel has the highest strength-to-weight ratio of any building material (Bliss, 2003).
From a health standpoint, steel has a couple of advantages, so it is sometimes used in non-toxic construction. Some people are sensitive to pine, so steel can eliminate its use (Bower, 1990).
Therefore, it is high time that an awareness is created amongst consumers about the enormous range of benefits that steel has to offer. There is now a need to look inside the walls and find the perceived value that steel offers and not search for it after one is ravaged either by fire, termite damage, nail pops or crooked walls.