October 2016

Welcome to ‘Stainless Solutions’ from IMOA. Each month, we will cover a different stainless steel issue with tips on design and specification, and links to technical resources.  This month’s issue looks at  roofing, one of the earliest applications of stainless steel in buildings, dating back to the early 1920’s.
Stainless Steel Roofing

Roofing was one of the first building applications for stainless steel. One US industrial roof was reportedly installed in 1924. The building is still in use and the maintenance department is not aware of any repairs. Industrial roofing remains a large and cost effective application for stainless steel.  A leaking roof can shut down a production line, which is very expensive. Stainless steel  is used when there are particularly corrosive plant or environmental conditions.

The first large high-profile roof was installed in 1930 on the Chrysler Building in New York. Stainless steel roofing remains a very popular choice for high visibility buildings because of its resistance to high wind loading, hail, fire and corrosion.  While other steels can also withstand high winds and hail when new, they can be weakened by corrosion over time.

Stainless steel roof finishes can meet both strict aviation low-reflectivity and solar reflective index (SRI) requirements. When properly selected for the environment, the SRI values of uncoated stainless steel do not deteriorate over time, because there is no corrosion to change the finish. At most, occasional dirt removal maybe required.  It has been used for airport, museum, residential, university, government and many other building types.

The mill-applied 2B and rolled-on dull matt finishes are the most commonly-used options for roofing. Electrochemically coloring over a dull finish, paint and various metallic coatings (i.e. tin/zinc, tin, and copper) are also widely used on stainless steel. With the exception of electrochemically coloring, which is applied to smaller panels, these finishes can be used for any roof style.

Roof aesthetic preferences and airport corridor roof reflectivity limits vary around the world. The 2B finish is the most reflective of these common options and any panel waviness from fabrication or thermal expansion will be more visible. In the Americas, that appearance is usually considered aesthetically undesirable and 2B use is typically limited to industrial or canopy roofs. In Europe and South Africa, waviness can be associated with a “handmade” roof and 2B is used on higher end buildings. It will not meet airport landing corridor reflectivity limitations in many parts of the world.

Gutters, flashing, downspouts, parapet coping and other smaller roofing system components typically have a 2B finish because it is the least expensive option that is readily available in light gauges.

The commonly used 2D mill-produced finish has been replaced by the less reflective rolled-on dull matt products developed for roofing in most markets.  It is now difficult to obtain 2D in the light gauges used for roofing.

Project Examples

Type 316 (UNS S31600, EN 1.4401) stainless steel batten cap roofing with a dull rolled-on finish was selected for Kowloon Train Station in Hong Kong because of the corrosive coastal industrial environment.
Photo credit: Catherine Houska

Described in the article Natural Forces (Modern Steel Construction 2003) this coastal US residence has Type 316 stainless steel roofing and wall panels. It will withstand the corrosive environment and 150 mph / 241 km/hr winds.
Photo credit: Catherine Houska

The Singapore Turf Club in Kranji is in a corrosive coastal environment with very high rainfall levels making a reliable roof material important. The curved undulating roof of the grandstand and walkways are Type 316 stainless steel because of its ability to withstand this environment.
Photo courtesy of Ewing Cole, photographer Erhard Pfeiffer.

The law courts in Antwerp were designed by Richard Rogers Partnership, VK Studio and Ove Arup Partners and have a spectacular roof composed of four roof “cones” made of Type 316L (UNS S31603, EN 1.4404) stainless steel. The roof seams are welded and the finish is 2B.

The undulations of the vegetated roof structure on the Paul Klee Center in Berne Switzerland mimic the surrounding countryside. Type 316L stainless steel with a matt rolled-on finish was selected. Even organic fertilizers are inherently corrosive making this a severe environment for materials.

The Gehry Partners designed Marqués de Riscal Vineyard in Elciego Spain used Type 316 stainless steel with a 2B finish for the dramatic curves of the hotel roof and a covered walkway.

The Scottish Parliament in Edinburgh was designed to rigorous sustainability and environmental standards for longevity. Type 316L stainless steel was used for the roofing, windows, façade and other exterior elements.

Design Resources

The following brochures provide more general design guidance and examples:

Stainless Steel for Rainwater Goods & Accessories (EuroInox)

Stainless Steel for Roofing (EuroInox)

Technical Guide for Stainless Steel Roofing (EuroInox)

Stainless Steel Library

Download a free Stainless Steel Library (zip file, 559 MB) with over 360 pdfs covering building and construction applications, selection, specification, fabrication, sustainability and other common questions.

Stainless Solutions e-newsletter archive

For previous issues or to subscibe to the e-newsletter, please visit the archive page.

Continuing Education – American Institute of Architects (AIA)

IMOA is an AIA continuing education system approved provider with eight 1-hour programs that are registered for both live face-to-face and distance learning credit.

1. Stainless Steel Sustainable Design
2. Bioclimatic Design With Stainless Steel Weather Screens
3. Stainless Steel Structural Design
4. Stainless Steel Specification For Corrosive Applications
5. Deicing Salt: Stainless Steel Selection to Avoid Corrosion
6. Stainless Steel Finish Specification
7. Advanced Stainless Steel Specification and Problem Avoidance
8. Specification of Stainless Steel Finishes and Grades For Corrosive Applications

For more information or to schedule a workshop contact Catherine Houska, 412-369-0377 or email chouska@tmr-inc.com.

What is IMOA?

IMOA (International Molybdenum Association) is a non-profit industry association, which provides technical information to assist with successful specification of molybdenum-containing materials. Molybdenum is an element. When it is added to stainless steel, molybdenum increases its resistance to corrosion caused by deicing salts, coastal atmosphere and pollution.

If you have a topic suggestion for a future issue of Stainless Solutions or need additional technical advice on stainless steel specification and selection, please get in touch here.

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