In architectural applications, stainless steel is often used because of its attractive appearance. Facades, interior cladding, lifts and escalators, handrails and parapets are some of the most typical areas of stainless steel use. The family of stainless steels, however, has more to offer than just good looks. Its technical properties make it an ideal choice for many other building applications, in which additional durability requirements are essential.
The advantages of stainless steel roofs are mainly related to three aspects:
- Maximum life expectation
The presence of air pollution highlights the need for corrosion resistant materials on buildings. The Chrysler Building in New York is clear proof that stainless steel is the ideal answer to this requirement. Built in 1929-1932, this building remains an outstanding testimonial for stainless steel in roofing and facade cladding.
- Minimum Maintenance
As maintenance costs continue to increase, it is important to bear these in mind right from the planning stage of a building. Due to its long-term corrosion resistance and its smooth surface finish, most stainless steel roofs, when designed and erected correctly, require very little maintenance.
- Low weight
Due to the high mechanical performance of stainless steel, the typical thickness of the material is lower than for most other metallic roofing materials. This can result in a lower overall weight after erection and therefore a lighter, more cost-effective supporting structure.
The Self-Repair Capability of Stainless Steel
Stainless steel is an alloy containing at least 10.5% chromium. This gives the steel an inherent ability to protect itself from corrosion. Chromium in the steel reacts with oxygen in the air and/or water to which the steel surface is exposed, and forms an invisible protective film of a chromium-rich oxide. If this layer is damaged, mechanically or chemically, it is spontaneously rebuilt if oxygen is present. Corrosion resistance is increased with higher chromium levels and, additionally, by adding molybdenum to the alloy.
The presence of nickel improves formability and weldability. Nickel-containing stainless steels work-harden on cold forming and can thus give the fabricated part an additional structural function.
The most commonly used stainless steels have a chromium content of around 17 – 18% and a nickel content of 8 – 10.5%. This is why they are known as “18/8” or “18/10”. These chromium-nickel grades are called “austenitic stainless steels”
Another family of stainless steels are mainly alloyed with chromium and possibly other elements like Titanium. These are called “ferritic” grades. For roofing purposes, 12 – 17% chromium grades with organic or metallic coatings can be used.
Besides the aesthetic benefits and the durability of stainless steel, architects, owners and developers may choose stainless steel for its physical properties such as:
- Heat reflection
Its smooth reflective surface provides stainless with excellent heat reflecting properties.
- Electric Conductivity
The continuous membrane of a seam welded stainless roof can eliminate the need for extra lightning conductors. Often it is enough to connect the whole roof to a good earth. Stainless steel roofs can also contribute to electromagnetic shielding, which may be required for buildings that house sensitive electronic equipment.
- Fire resistance
The melting point of stainless steel is around 1500°C, which is much higher than for most other roofing materials, e.g. Al 660° C, Zn 419° C, Cu 1083° C.
Choosing stainless steel roofing provides a range of design possibilities. Stainless steel products are available in many different finishes, the range of surfaces varies from subdued greys, to bright mirror –type finishes. The steel will also change its appearance as it reflects subtle changes in lighting conditions. Therefore, stainless steel is a highly beneficial choice for your roofing solutions.
Source: Euro Inox – European Stainless Steel Development Association
Jessica R // Editor SMC