Steel is an awesome material with many benefits, which is why Whirlwind Steel sells steel buildings. But we also understand nothing is perfect. Every building material has pros and cons. We may stress the pros most of the time, but we also must address the cons.
Like any construction material, metal suffers from a couple of conditions that could result in weakness. Most of the disadvantages, however, can be overcome with a little thought.
What are the disadvantages of metal buildings, and how can you rectify or avoid them?
High Initial Costs and Low Availability
The cost-effectiveness of building with steel is not typically found in its initial purchase price. If you compare the cost of materials alone, steel will be higher than wood, concrete, brick or stone. Unless there is a shortage of wood or other material required to make these basic construction materials, you will probably pay less for them than you would for the amount of steel required for your project.
In certain countries and some economic climates, steel may not be available in the volume necessary to construct a building. The cost of transportation may be too high because the metal must be shipped long distances. The price may increase due to demand in areas recovering from a disaster or experiencing rapid development.
Transportation routes disrupted by war and civil unrest can create further shortages of non-native materials. If steel mills and other manufacturing facilities become damaged, a shortage of the materials will be felt quickly.
Uncoated metal rusts, that’s all there is to it. Steel that is not protected by galvanization or a finish corrodes in the presence of moisture. In coastal areas, where there are high levels of salt, rusted metal is not uncommon.
The problem with rust and corrosion, aside from the aesthetics, is that it weakens the metal over time. Eventually, the metal will fail and require replacement. Rust essentially eats away at metal, weakening its molecular structure and leaving behind a brittle substance that lacks any strength or protective property.
However, steel typically is not used before it is coated. Nearly all steel is galvanized, a treatment that coats the outer steel skin with a sacrificial layer of zinc. As corrosive materials come into contact with the coated steel, the zinc will oxidize first. It isn’t until the zinc layer is exhausted that the iron will be susceptible to corrosion.
Galvalume steel, which is steel coated with an aluminum-zinc coating, is even less susceptible to moisture. As long as the galvanic layer is intact, the steel is protected.
Special paint coatings also protect against oxidation. Paint is made up of pigments, resin and a solvent. Acting as a system, the pigment, or color, is mixed into a solvent for liquidity. Once painted on the surface, the solvent evaporates as the paint dries, leaving behind the color embedded in a resin that forms the desired appearance on the surface of the metal.
As long as the coating remains intact, the metal beneath is protected from oxidation. While the paint may fade or chalk, these are merely aesthetic issues and do not impact the durability of the metal itself.
Steel is, indeed, less flammable than other materials, but if exposed to fire for a long period, it can be weakened by sustained high temperatures. At 400 degrees C, plastic deformation under load occurs, creating large deflections in the steel members. Any stresses on a main member transfer loads to other members, potentially resulting in collapse.
Steel transfers heat extremely well, and flammable materials that come into contact with hot steel can catch fire and cause it to spread, even though the metal itself is not alight. It’s possible that heat from a portion of a structure on fire could be transferred to a non-burning area, increasing the ambient heat overall.
Additional fire-proofing may be required for complete safety. Expanded mineral coatings, concrete and intumescent materials have all been used as fire-resistant barriers. Some fireproof coatings for steel can be quite expensive, adding to the cost of the structure.
Steel may also be embedded in gypsum board or block, masonry block or clay tile to protect it from heat. Certainly, a sprinkler system is often required by building code, regardless of the material used to build the structure. All of these added solutions require maintenance.
Fatigue and Fracture
Steel members are susceptible to fatigue. There may be variations in the tensile strength of the members, causing needless tension and reducing overall strength.
Also, when steel loses its ductility, it can become brittle and fracture. Eventually, the structure will buckle. To protect against buckling, additional steel columns may be added to stiffen the primary frame.
Sourcing the steel from a reputable company can reduce the variability in quality within and between steel members.
While steel is a versatile material, it is not easy to make field corrections if one or more components do not fit properly. Most metal building manufacturers perform strict quality assurance processes to ensure all parts of a building solution fit correctly, but in the event they do not, there is no way to "make it fit" in the field without introducing more weakness into the structure.
Waiting for a replacement from the manufacturer can introduce an unacceptable delay in the schedule, however, so some contractors prefer to use wood frames so that potential fit issues can be resolved onsite.
The disadvantages of metal buildings do not outweigh the advantages of building with steel, far from it. Each issue can be mitigated through the use of other materials and care in manufacture. As far as material fatigue, there is no construction material that is invulnerable to fatigue. In fact, it could be argued that the durability of steel is better than wood or concrete.
Wood, concrete and masonry are all more prone to splintering and cracking, particularly under seismic activity or simple thermal movement. Fire also impacts these materials. Obviously, wood is highly flammable, but concrete can explode in high heat if the moisture within has not been allowed to evaporate properly.
There is no construction material available that is completely safe, that provides all the advantages and none of the disadvantages of steel or other construction materials. Steel comes the closest and the price disadvantage disappears as the total cost of ownership is considered.
Don’t let the disadvantages listed here keep you from using the best construction material available.