Can Your Roof Go the Distance? 

Great for the environment and easy to work with, InvariMatte® stainless steel is the perfect choice for beautiful, durable, energy-saving roofs.

InvariMatte® has a low glare texture which is easy on the eyes, even in direct sunlight, which makes it ideal for roofing applications. While it does have a muted appearance, there is just enough reflection going on to take on the colors of the environment around it. Looking bluish gray on a blue sky day, it takes on warm tones at sunset. InvariMatte® retains its original beauty over time without developing a patina. Its unique finish, which involves no coatings, is rolled directly into the surface of the metal. This process not only controls finish variability more closely than any other surface treatment available on bare metal, it also results in a visual effect that is extraordinary. The low gloss InvariMatte® finish is ideal for roofing applications, wall panels, coping and trim. Perfect for designs ranging from modern to historic renovations, its enduring beauty truly goes the distance.
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The Case for Stainless Steel 

The proponents of stainless steel finishes for architectural applications exude the same evangelical loyalty as longtime users of Apple computers. In their hearts, they know they have the superior product, regardless of where it ranks in terms of market share, and they fervently want to convert you to their way of thinking.

To be fair, the champions of stainless steel finishes possess a strong case and can point to many iconic examples of their product—buildings and other structures that have stood the test of time for their longevity, beauty and prestige. A favorite word among stainless steel advocates to describe their product is “timeless.”

New York City is home to the two most famous stainless steel projects in the United States: the Chrysler Building (1930) and the Empire State Building (1931), each of which was able to lay claim to being the tallest building in the world at the time of its completion. Chrysler was the tallest for about nine months until it was overtaken by the Empire State Building, which held the title for more than four decades.

The Chrysler is one of the 20th century’s architectural trophies, a classic embodiment of the Art Deco style, and also was the first large, high-profile, stainless steel application in the world. The building’s distinctive ornamentations model themselves on features then being used on Chrysler automobiles. The stainless steel gargoyles anchored on the corners of the 61st floor are replicas of the 1929 Chrysler hood ornaments. The stainless steel arches represent hubcaps. The six rows of stainless steel arches, created using standing, batten and flat lock seams, are topped with a stainless steel spire.

One of the hallmarks of stainless steel finishes is its minimal need for maintenance. In any urban or industrial setting, all that is usually necessary is a washing with detergent and water or with one of the commercial stainless steel cleaners. In many circumstances, however, washing can be accomplished by the action of rain and wind.

In the 78-year history of the Chrysler building, the exterior has been cleaned only twice, in 1961 and in 1995. The building is considered to be in very good condition. There are some small dents from the cleaning equipment and minor pitting above the flu pipe and on the 61st story balcony. Neither adversely affects the roof integrity and the pitting could be removed with simple polishing.

The other landmark building from that era, the Empire State Building, boasts an exterior which is stainless steel, gray limestone and dark gray aluminum. It has been cleaned only once—in 1995—and is reported to be in excellent condition, with no problems ever attributed to the stainless steel other than the need to replace some panels following an accidental plane crash into the building in 1945.

There have been countless other distinctive examples of stainless steel buildings and structures, including the Petronas Twin Towers in Kuala Lumpur—the tallest buildings in the world for a time when they were constructed—Neur Zollhof in Dusseldorf, Germany; the Mapfre Tower in Barcelona; the Housing and Commercial Development, Lucerne, Switzerland; the Sun Life Centre in Toronto; the Gateway Arch in St. Louis; the Mellon Arena in Pittsburgh; the Printemps department store in Osaka, Japan; the Inland Steel Building and Millennium Park in Chicago; JIn Mao in China; the Walt Disney Concert Hall in Los Angeles; Washington National Airport; Canary Wharf and the Jubilee Line in London; and LeGeode in Paris.

More recently, in just the past several years, stainless steel has been used in projects involving public institutions such as Roger Williams University’s student union building in Bristol, Rhode Island; the University of Maryland new Dental School building; and a project that has received national attention, the recently dedicated United States Air Force Memorial in Arlington, VA. The website for the Specialty Steel Industry of North America says the new memorial “ranks as one of the world’s largest structural applications of stainless steel, along with the Dublin Spire in Ireland and America’s largest memorial, the Gateway Arch.” The Air Force Memorial, located on a promontory just west of the Pentagon, features three curved spires that arc up to nearly 300 feet in the air.

Stainless steel is finding its way in a number of other construction categories, such as airports. Such projects recently have included work for the Jamaica AirTrain JFK Terminal, and at airports in Dallas-Fort Worth, Atlanta, Detroit Scottsdale, AZ and Raleigh Durham—as well as an extensive project now underway at the Doha airport, which soon will boast the world’s largest stainless steel roof.

Why Stainless Steel?
The origin of the name is self-evident: stainless steel does not stain, corrode or rust as easily as ordinary steel. The metallurgical definition of stainless steel is an iron-based alloy with a minimum of 10.5 percent chromium content. Chromium produces a thin layer of chromium-rich oxide on the surface of the steel known as the passive layer. This reduces the possibility of corrosion of the surface. Increasing the amount of chromium gives an increased resistance to corrosion. Other alloying elements are added to enhance their structure and properties such as formability, strength and cryogenic toughness. These include nickel, molybdenum, and nitrogen.

However, this is not to say that stainless steel is invincible. In some circumstances it can corrode. To borrow a phrase from the British Stainless Steel Association , “it is 'stain-less' not 'stain-impossible'.” In normal atmospheric or water-based environments, stainless steel will not corrode, but in more aggressive conditions, the basic types of stainless steel might experience some corrosion. Therefore, in those situations, a more highly alloyed stainless steel would be required for the job.

Product Characteristics
Stainless steel can be selected for use for a number of different reasons, not just its resistance to corrosion. These include:


Aesthetic Qualities – Different stainless steel finishes, along with their processing methods, can affect the visual appearance of metalwork in terms of the following:
Textures – Stainless steel comes in a variety of surface finishes. A project design team can choose textures from dull to bright (spectral gloss at 85° from 8 to 99 on a scale of 1 to 100) and smooth to rough (Ra or average surface depth <10 to >500 micro-inches). Stainless steel can even be polished to a satin or mirror finish. Processing methods include abrasive polishing, cold rolling, coining, embossing, media blasting, and colorizing. Geometric finishes and colorized stainless steels are also available.
Visual Uniformity – Finishing methods also vary in terms of visual uniformity. The design team should take this into account. For example, elevator access doors are quite critical in terms of ensuring a pair of doors installed side-by-side will dependably look the same.
Flatness – Factors such as gauge and finishing methods have an impact on flatness.
Fire Resistance – Stainless steel exhibits better fire resistance than ordinary carbon steel, especially better strength retention at elevated temperatures. In addition, many anti-corrosion coatings are fire hazards or the materials themselves have a low melting point.
Cleanability – Stainless steel is easier to clean in terms of bacteria removal.
Weight Savings – As thinner sections can be used, more innovative design structures can be created, saving money on foundations and platform weights.

Most types of stainless steel used in architecture include a percentage of nickel, and manganese, molybdenum, or other elements. Architectural stainless steel finishes are suitable for a variety of interior and exterior applications, including roofing and wall panel systems, composite panels, elevators, coping, trim, flashing, doors and cabinets. From its inception, it became the preeminent material for projecting a progressive, modern image. That still holds true today, and the range of design options for architects has increased many fold since the 1920s.

Today’s stainless steels are produced in large volumes, offering a wide variety of steel grades and finish options, including color and texture. Architects are attracted to the product for the benefits already mentioned—atmospheric corrosion and wear resistance, strength, durability, fire resistance, cleanability, range of finishes—and for its product forms, which include structural components, precision castings, wire, cloth, panels and tubular products.

Stainless steel’s resistance to corrosion carries two attached benefits. There is no need to compensate for loss of strength due to metal deterioration, and replacement costs are virtually nonexistent. Any building owner interested in the long life of a building, rather than just a short-term gain, will be drawn to stainless steel because of its lifecycle cost payback. Stainless steel finishes last the life of the building and are low maintenance, never requiring, for instance, a fresh coat of paint.

Stainless steel’s aesthetic quality is well known. It is notable for its beauty and the ease with which it blends with other materials. It has a subtle sheen which complements, reflects and highlights surrounding materials. Because it won’t corrode, its appearance is permanent and there is no danger of streaking or staining other materials.

Stainless is one of the strongest of metals. Tensile strengths of 75,000 to 125,000 psi (or higher if needed) allow the use of gauges much lighter than are usually needed in other metals, Sturdy design elements, fabricated from thin sheets of stainless steel, can combine light weight with strength. It is produced in virtually all standard metal forms and sizes, plus many special shapes.

Stainless Steel’s Strength
Architects are catching on to stainless steel’s strength and the option to reduce gauge. Research shows that a Type 304 stainless steel sheet, for example, has at least three times greater tensile strength than aluminum sheet. This fact is percolating throughout the building industry to the point that there is now a growing tendency among architects and specification writers to write performance type specs rather than construction type specs. The advantage? Reduced costs. Construction specifications requiring stainless steel sections to be as thick as aluminum ones put an unnecessary cost disadvantage on the stronger stainless steel. However, performance type specs are based on putting strength where it is needed.


The Green Material
Stainless steel is a green material. It is 100 percent recyclable. An average stainless steel object is composed of 60 percent recycled material—25 percent of that originating from end-of-life products and 35 percent coming from manufacturing processes. Furthermore, the fact that stainless steel will last the useful life of the building limits its impact on the environment—and usually results in the least long-term costs to the building owner.

Life Cycle Costing
It’s because of this last reason that manufacturers and distributors of stainless steel believe that life cycle costing should be taken into account when designing for permanence and selecting materials for architectural applications. The Federal Highway Administration issued a report in 2001 estimating that in the United States alone, Americans spend about $550 billion a year combating metallic corrosion. Of that cost, $113 billion per year is spent on construction related metal failures ranging from roof perforation to replacement of components that have become aesthetically unattractive. Other studies conducted in recent years by both Batelle Laboratories and the National Association of Corrosion Engineers (NACE) concur that in the U.S. alone, we spend about $300 billion per year fighting metallic corrosion. The Batelle study estimates $100 billion of those costs could be avoided with proper material selection.

The history of stainless steel traces back through many discoveries and innovations that were set in motion in the 1820s by English and French scientists. Eventually, after decades of metallurgical developments in England, France, Germany and the United States, stainless steel’s birth occurred in 1913 when Harry Brearley of England created a steel with 12.8% chromium and 0.24% carbon, widely considered the first ever stainless steel.

Today, there are more than 150 grades of stainless steel, with about 15 to 20 being the most popular. The alloy is milled into sheets, plates, bars, wire and tubing for a wide variety of products and applications. The architectural possibilities for stainless steel have advanced beyond the “decorative” – it is now a vital fabric of many buildings, including its use as roofing, cladding, wall panels, composite panels, and even reinforcing bars for concrete structures for which a long design-life is required.

Stainless steel has arrived. With all of its advantages, architects, specifiers and building owners no longer ask if they can afford stainless steel – instead they now realize that, in the long run, the more pertinent question is, “Can we afford to be without it?”
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How to Handle the High Cost of Metals 

The escalating cost of building materials is challenging the construction industry to manage costs, including anyone designing with metals, especially “exotic” types, in order to achieve beautiful and sustainable structures. As far as metals are concerned, prudent steps can be taken to minimize exposure to rising prices.

Make Commitments Early
The long process from concept to completion works against the estimator. Material prices increase over time, which negatively impacts the budget. However, trying to play the market by anticipating a decline in prices before placing your order is a mistake. If you are highly skilled at predicting market prices, you should become a commodities trader, but if you are a contractor, installer or fabricator with a metal project in your backlog, you should commit to the work at the earliest possible moment. Of course, when prices are declining, dragging your feet can put money in your pocket, but if you are inclined to speculate in times of price volatility, you are better off on Wall Street.

Secure Funding For Stored Materials
In accepting the early commitment argument, the natural question is: “Who’s going to pay for the metal before it’s needed?” This issue needs to be communicated early in the game. Ideally, the owner should be prepared to provision the cash. The bid documents should clearly reflect this.

Do Value Engineering Up Front
In the last couple of years, as metal prices have continued to move upward, a significant number of metal products – stainless steel, zinc, copper and even aluminum and steel – have been value-engineered to cheaper materials. While downgrading materials may have “saved” money upfront, the extra time spent searching for cheaper alternatives subjects the budget to escalating prices. Moreover, substituting materials that require maintenance or replacement within the life span of the building may actually increase the lifecycle cost. The owner is best served when an appropriate metal with a long lifecycle and a low lifecycle cost is specified for the project and when all parties stick firmly to the plan.

Communication is critical. If an owner doesn’t understand your rationale or see the value in the materials you selected, state your case. There is much to consider when selecting the right metal for a particular project. Environmental conditions, the structure’s end use, and the amount of anticipated maintenance are just a few. And there are many other considerations once the particular metal is selected, such as grade and finish. You can’t assume that the owner has taken all of those factors into account. Examples of past projects, research, testimonials or information from a material provider or consultant can help solidify your arguments. After all, who wouldn’t want a metal that would need little or no maintenance and would last the life of the building?
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The Use of Metal on Airport Exteriors is Taking Off 

Metal is showing up more frequently on newly-constructed airport exteriors across the country. The trend signals a see-and-avoid juncture for airport construction specifiers mindful that some metal products are less suitable for airport settings than others – those that have reflective properties, require paint, or corrode when exposed to jet fuel emissions. Not so with Contrarian Metal Resources’ InvariMatte®, a corrosion-resistant, uncoated stainless steel finish with low glare and a long lifecycle.

The InvariMatte® finish recently has been used on several major airport projects in the United States, including the Jamaica AirTrain JFK Terminal in New York, an expansion at Detroit Metropolitan Wayne County Airport in Michigan, and the Scottsdale Aircenter in Arizona. InvariMatte® was chosen for these projects because of its dependable characteristics and uniform appearance.

In addition to sun, wind and precipitation, airport exteriors are continually exposed to jet fuel residue, earth-rumbling engines and the repercussions of heavy traffic. The materials used to construct these exteriors must stand up to these elements and maintain an aesthetic standard. Stainless steel accomplishes both goals.

Corrosion-Resistance
InvariMatte® resists the threat of corrosion from atmospheric conditions and trapped moisture.

Data collected from the Nickel Development Institute indicates that aluminum, a common alternative to stainless steel, corrodes several times faster. While a layer of paint is effective for extending the life of an aluminum panel, it can actually have a detrimental effect on corrosion resistance if that layer is breached and moisture is trapped at the metal interface. Incidental damage to roof panels – punctures in the paint, or dents and dings – can easily occur from routine maintenance or weather events, such as hailstorms. If moisture and contaminants - like sulfur dioxide and chlorides - are trapped at the metal surface, rapid deterioration, known as crevice corrosion, will occur.

Fortunately, with InvariMatte®, no paint is needed, allowing the natural beauty of stainless steel to shine through.

No Chance for Paint Deterioration
Aside from physical damage done to them, painted surfaces do not stand up well in an airport environment because of jet fuel residue. Kerosene-based fuels will act as solvents when particles come in contact with painted exteriors. While some floor paint formulations are resistant to jet fuel, none is available for coil-coated applications. More to the point, however, is the fact that “resistance” to jet fuel does not equate with “imperviousness.” The InvariMatte® finish is able to make the claim that it is impervious to jet fuel.

Low Glare
In addition to being visually uniform, Contrarian’s InvariMatte® has low reflectivity compared to typical stainless steel finishes. For that reason, it can be used on airports as prominently visible exterior walls and roofs with no risk of glare or reflection that could compromise a pilot’s sight. InvariMatte® has lower gloss (<20 at 85 degrees Fahrenheit) than many paint finishes.

Low Lifecycle Cost
Considering the high cost of service disruption at an air terminal, not to mention security issues, a permanent stainless steel roof system is a logical and cost-effective choice. While titanium will perform beautifully from a sustainability standpoint, it’s expensive in comparison to stainless steel. Likewise, a less costly alternative, aluminum, painted or not, requires maintenance or replacement at some point during its lifecycle, which makes it more costly overall.

Type 304 or 304L InvariMatte® stainless steel can be expected to last the useful life of an air terminal building with little maintenance. Gutters should be kept clear and panels may need to be cleaned for cosmetic reasons, but these are minimal necessities as compared to alternative products.

Recent Airport Applications for InvariMatte®
Jamaica AirTrain JFK Terminal in New York is a $389 million multimodal transfer point that links the new light rail system from JFK International Airport to the Long Island Railroad, New York City Transit subway lines, and ground transportation centers. About 8,500 of the airport’s 32,000 daily passengers arrive or depart from the terminal.

Reflectivity was a concern not only for pilots and airport personnel, but also for those who live and work in surrounding high-rise buildings and condominiums. “InvariMatte® is a sensible choice as a cladding material in dense urban environments,” says Contrarian Metal Resources President Jim Halliday. “While stainless steel addresses corrosion and paint failure concerns due to smog and jet fuel residue, other stainless steel finishes are just too bright to be used in glare-sensitive locations like transportation centers.”

InvariMatte® was also specified for its longevity and low-reflectivity at Detroit Metroploitan Wayne County Airport and Scottsdale Aircenter. When construction began in 2001 at the $1.2 billion Edward H. McNamara Terminal at Detroit Metro, it was one of the largest construction projects in the United States. The redevelopment and expansion project solves operational and structural problems and readied the airport for forecasted growth in air traffic and passengers.

Scottsdale Aircenter, a full-service Fixed Base Operator at Scottsdale Airport, opened in 2003. Construction is underway on an expansion project that will add more than 100,000 square feet of hangar and office space.

InvariMatte® is a non-directional, low gloss, uniformly textured stainless steel finish designed for architectural applications. While its lower reflectivity lends itself to roofing applications, it can be applied to wall panels, coping and trim. The superb consistency of this finish results in excellent panel-to-panel matching. Since InvariMatte has no coatings to deteriorate, it will last indefinitely with little maintenance. InvariMatte is readily welded or soldered and available in coils and cut lengths up to 288 inches and widths ranging from 0.75 to 49 inches. Because stainless steel is dimensionally stable up to 2000-degrees Fahrenheit, InvariMatte® provides an added measure of protection in the event of a fire. Contrarian Metal Resources offers a 30-year warranty on Grades 304, 304L, 316, and 316L.
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The Do’s and Don’ts of Stainless Steel Roofing 

For the architect, panel manufacturer, fabricator, installer or contractor considering a stainless steel roof, you can expect a beautiful, permanent roof system that will be very economical in the long run—if you rely on a competent architectural metal supplier and don’t make the assumption that stainless is like any other metal. Here are some do's and don’ts to guide you:



Do…
Recommend stainless steel where sustainability is important because it will last. On buildings that are designed to last longer than the anticipated life of other roofing materials, stainless steel is less expensive in the long run. While stainless steel may not make economic sense on a strip mall, for example, it is possible to install a permanent stainless steel roof that will save the owner repair and replacement costs in the future. When life cycle costing is conducted, including acquisition, maintenance, service disruption and disposal costs in present value terms, stainless steel is hard to beat.

Use a low glare stainless steel finish, like Contrarian Metal Resources’ InvaiMatte® where a highly reflective surface, as most stainless steel finishes are, will pose a problem. InvariMatte has been used on a number of airport terminals where glare poses a safety risk. In addition to promoting safety, a low glare finish will be less apt to show oil canning, or shape deviations in the panel work.

Use a uniform surface finish that is designed for architectural applications. Aside from having a low glare property, InvariMatte is also quite uniform, allowing for a good-looking bare metal installation.

Use a grade of stainless steel that is appropriate for the environment. Coastal environments and sites where deicing salt is used in close proximity will usually require Type 316 stainless steel. Type 304 is appropriate in most other locations. The low carbon versions of these grades (T316L/T304L) should be specified on parts that will be welded. Other grades may be considered, depending on the environment. If you follow our earlier advice with regard to selecting a competent supplier, you can rely on their expertise in grade selection. If you choose to work with Contrarian Metal Resources, a 30-year limited corrosion warranty will back up our material recommendation.

Detail the system so that it drains well. While stainless steel is very forgiving when it is exposed to moist conditions, good water and vapor management will promote the longevity of all of the affected materials in the system.

Use proper tooling for stainless steel fabrication. The mechanical properties of stainless steel are higher than mild carbon steel, aluminum and other metals that are used for roofing. The most significant difference the panel manufacturer or fabricator will notice during forming is a higher modulus of elasticity or greater “spring back”. In order to overcome this issue it is often necessary to have a combination of more horsepower and more tool sets in the roll forming operation. It is also important to have sufficient tooling harness so that the work rolls do not wear prematurely. Further, seaming tools need to be of sufficient capability to form stainless steel.

Monitor tool wear to ensure good results. Worn tooling bears the risk that free iron molecules will imbed in the surface of the stainless steel. If this occurs, it will cause the stainless steel to corrode, manifesting as red rust on the surface of the material. It is necessary in this case to remove the rust with a solution like dilute citric acid.

Remove heat tint from welding operations. Left untreated, this carbide-rich scale will propagate corrosion. Cryogenic blasting is an excellent method of scale removal. Pickling paste is also effective. Fabricators and installers often grind the scale off, but this method is not as effective and the repair area is much more reflective than the parent metal surface, particularly if a low glare finish has been used.

Strip the protective vinyl film at the earliest opportunity in the field, once other subcontractors are out of the area. First of all, a good architectural metal supplier will apply a strippable film that is capable of withstanding outdoor exposure for a period of weeks. This is not to say that you can leave the film on indefinitely. Assuming exterior-grade vinyl has been supplied, it is prudent to leave the film on the panel work throughout the installation process in order to protect the surface from contamination by construction debris, including wasted carbon steel fasteners, welding swarf, tar and paint. Strip the film as soon as the risk of contamination has passed. This will minimize the need for final clean-up activity upon owner inspection.


Don’t…
Abut dissimilar metals without evaluating the risk of bi-metallic, or galvanic corrosion. This is of particular concern where moisture can reside and where the metals are substantially different in terms of electrode potential. Fasteners should be stainless steel of equal or nobler grade.

Rely on solder for strength. While stainless steel is solderable, it is best to use solder for small connections that need to be made for water management purposes. However, in a shear condition, a stainless steel solder joint will fail.

Use muriatic acid, chloride-based cleaners or abrasives when cleaning stainless steel. Instead, you should use a mild detergent (ammonia –based is fine) and rinse for general clean-up. Acetone will address grease, tar and fresh paint. Use MEK on dried paint. Free iron contamination (rust) will sometimes respond to mineral oil, but imbedded iron particles will likely require dilute citric acid, followed by a rinse.

If you start with a competent architectural metal supplier that can help you select a grade and finish that is appropriate for the application, and follow these dos and don’ts, you can be assured of good results. While stainless steel costs more up front, in the long run the owner can be spared the cost and inconvenience of replacing the roof.
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