The product is a 55% aluminum-45% zinc alloy coated sheet steel developed by Bethlehem Steel and sold commercially under the trademark Galvalume®, starting in June 1972. Bethlehem Steel later licensed other major steel companies to produce and sell the product using its patents and technology. In North America, the Galvalume® trademark is used by Bethlehem Steel, Dofasco Inc. (Canada), National Steel Corp., U.S. Steel and Wheeling-Nisshin, Inc. In Central and South America, Industrias Monterrey (Mexico) markets the product under the trademark Zintro-Alum, while Galvak S.A. de C.V. uses the trademark Galval. Steelscape, Inc. uses the trademark GALVALUME®. All of these products are the same generic 55% Al-Zn coated shee steel made by the same process using the same technology.
Both Galvalume® and galvanized sheet steels are made by a "continuous hot dip" process. Coils of cold rolled steel are welded end-to-end and processed continuously on the coating line at speeds up to 600 feet per minute. The uncoiled sheet is first cleaned to remove rolling oils and mill dirt, and to reduce surface oxides so that the surface will accept the coating. These continuous sheets are first fed into a molten coating bath contained in an open top, brick-lined heated pot. The sheet then passes around a roller submerged in the coating bath and exits the bath vertically, pulling out with it an envelope of the coating material. As it exits, the sheet proceeds through a pair of opposing air knives, which are positioned above the bath and equidistant from the surface of the sheet. Most modern production lines have a coating thickness gauge feed-back control, which automatically adjusts knife air pressure and position to ensure that a uniform coating is applied. Various finishing steps are carried out to complete the process, after which the sheet is wrapped around a reel into a coated steel coil.
Galvalume® sheet is an ideal material for roofing because of its extraordinary outdoor corrosion resistance and resulting long life. It can be readily rollformed into a variety of panels, as well as formed and stamped into tile and shingle facsimiles. It can also be factory painted to impart color and extend durability. Most important, it can be used in modern day steel roof designs which are strong, yet light weight. And unlike conventional nonmetallic roof systems, Galvalume® sheet roofs won't crack and peel when subjected to the sun and weather.
Galvalume® sheet is made to meet ASTM Specification A792. This specification covers a number of requirements, including coating weight. AZ50 and AZ55 are the English unit coating weight designations indicating that, respectively, 0.50 ounces per square foot and 0.55 ounces per square foot of the aluminum-zinc alloy coating have been applied to both sides of the Galvalume® sheet. Converting these coating weights to coating thickness, AZ50 is equivalent to about 0.8 mil (0.0008") on each side of the sheet, and AZ55 to about 1.0 mil (0.001") on each side. In metric units, AZ150 is equivalent to about 20 microns and AZ155 to about 25 microns on each side.
Galvalume® sheet has good heat and sunlight reflectivity. Its bright reflective surface makes it an ideal material for roofing. During the summer it makes buildings cooler by efficiently reflecting away sunlight and reducing the amount of heat transmitted into the building. Likewise, it makes buildings warmer in the winter by reflecting inside heat from the underside of the roof back into the building. This good thermal reflectivity translates into energy savings by reducing cooling costs in the summer and heating costs in the winter. Tests have shown that only half as much heat from solar radiation is transmitted into a building fitted with a Galvalume® roof compared to a galvanized roof, and almost one-third less heat compared to a terra-cotta roof.
Leaking conventional, flat nonmetallic roofs are the biggest problem on nonresidential buildings for architects and building owners. Conventional roofs made with organic materials deteriorate even under normal environmental conditions. They embrittle from the heat and ultraviolet radiation from the sun. Then, as result of temperature fluctuations, they develop cracks, splits and tears. Finally, because they are flat, ponding water inevitably penetrates these brittle, cracked systems and leaks into the building, causing damage to goods and disrupting activities inside the structure. Leaks can be patched early in the life of the roof, but as time passes, leaks become more frequent and an expensive replacement of the roof is required. Such replacements often require tear off, extra labor and even a temporary building shut-down. Galvalume® standing seam roofs (SSR) offer a weather tight, maintenance-free roof system that will last for decades on commercial, office and factory buildings. Galvalume® SSRs are economical to install, leak proof, maintenance-free, energy efficient, noncombustible and long-lived.
Regarding warranties, a purchaser needs to consider the two types of Galvalume® roofs that are used -- structural and architectural systems. Structural systems are those, such as SSR, that are installed directly on the roof structural system (i.e., purlins), without decking. These are low slope systems, up to about 1:12 pitch, using bare, heavier gauge Galvalume® steel sheet. Use in this application is guaranteed for 20 years. (Some roofing manufacturers also warrant their roof systems for weather tightness.) Architectural Galvalume® roofs are those used in applications in which the roof is being used not only for protection against the weather, but also for its appearance. Because architectural roofs are visible from the ground, they are used as a design feature of the building. Such systems are used at high slopes, usually up to 4:12, for both residential and nonresidential buildings. In most cases the Galvalume® panels are prepainted in a wide range of colors using today's high performance paint systems. Regarding warranties, a purchaser needs to consider the two types of Galvalume® roofs that are used -- structural and architectural systems. Structural systems are those, such as SSR, that are installed directly on the roof structural system (i.e., purlins), without decking. These are low slope systems, up to about 1:12 pitch, using bare, heavier gauge Galvalume® steel sheet. Use in this application is guaranteed for 20 years. (Some roofing manufacturers also warrant their roof systems for weather tightness.) Warranties cover both the Galvalume® sheet and the paint system. Most Galvalume® producers give the same warranty for the Galvalume® steel substrate for prepainted roofing as that for bare roofing. Most producers also give a 5 year warrantee against chalk, fade and peel of the paint system. Paint companies and coil coaters typically extend the paint warranty as much as five years beyond the 20 year Galvalume® sheet producer warranty, depending upon the paint system and environmental conditions. Galvalume® sheet producers and roof manufacturers should be contacted for specific requirements for their warranties.
Galvalume® sheet has been successfully used in roofing applications for more than 25 years; it has been evaluated in outdoor R&D tests for well over 30 years. Based on these tests, in which corrosion weight losses were measured and compared with galvanized, Galvalume® sheet is projected to outlast galvanized sheet (with an equivalent coating thickness) in various atmospheres by up to nine times. Likewise, recent inspections of 82 low slope Galvalume® roofs up to 22 years old in the eastern U.S. confirms the R&D results. These roofs are in excellent condition and are projected to last 30 to 40 years before requiring major maintenance.
Wood or steel decking is normally used for prepainted Galvalume® architectural roof systems on both residential and nonresidential applications, but it is not recommended to install the panels in direct contact with the decking. Instead, 30 pound felt, or an equivalent, should first be installed on the decking and the roof panels then installed over the felt. For residential applications, the roof panels would be installed over roofing felt on wood decking for new construction applications, or in applications in which the old shingles would be removed from the deck. Roofing manufacturers should be contacted for design and installation details both in warmer regions where condensation can occur under roof panels, and also in cold regions where snow, ice and water can collect at eaves and valleys and leak into the building.
Contact with pressure-treated wood or, for that matter, any wet lumber is not recommended for either bare or prepainted Galvalume® sheet. Treated lumber contains chemicals that protect the wood when buried in soils. Direct contact between wet treated lumber and Galvalume® sheet creates a corrosion cell and the corrosive chemicals leaching out of from the wood accelerates this process. All rooftop ancillaries, such as air conditioners, should be mounted with factory-made mounting accessories compatible with Galvalume® sheet (roof curbs, for example). Some HVAC contractors commonly mount rooftop air conditioners on pressure treated landscape ties. Direct contact of these ties with the Galvalume® roof causes corrosion of the aluminum-zinc coating. Even drainage from pressure treated lumber onto Galvalume® sheet should be avoided.
The many benefits offered by new and retrofit Galvalume® standing seam roofs (SSR) over traditional nonmetallic roofs translate into both direct and indirect cost savings. A retrofit Galvalume® SSR installed on a light weight structural system over an old, leaking nonmetallic roof is a lower cost long term alternative and, in many cases, a lower initial cost alternative if tear-off of the old nonmetallic roof is required. Benefits that translate into related cost savings result from the installation of additional insulation under the Galvalume® SSR, avoiding tear-off so that activities inside the building are not disrupted and disposal of nonmetallic material is not necessary, and the ability to schedule retrofit installations on a year-round basis in almost all climates. The initial cost of a new, low slope Galvalume® standing seam roof will generally be more expensive than a traditional flat nonmetallic roof, such as a built-up roof. However, if long term life cycle cost is considered, say, up to 25 or 30 years, the Galvalume® SSR will cost less than a nonmetallic roof. That's because initial repairs for leaks on nonmetallic roofs are not unusual after only 8 or 10 years, and replacement by tear-off may be required after about 15 to 20 years. So, over the long term, a new Galvalume® SSR will cost less than a traditional nonmetallic roof. This lowered life cycle cost, resulting from the minimal maintenance required by a Galvalume® roof, is what makes steel roofing an appealing, affordable and long-lasting alternative to traditional asphalt, wood, tile and slate roof coverings.
Durable and strong One of the most thermally efficient roofing materials available today Superior corrosion resistance Attractive Excellent resistance to impact Excellent flexibility in design, can be curved, for truly individual designs Easy maintenance Weather tight and secure when installed to manufacturer's specifications Galvalume sheets from DomodRoof is also used for wall cladding. Wall cladding made from GALVALUME® steel is available in a range of attractive profiles. It is lightweight, versatile and attractive and has excellent corrosion resistance. Durable and strong • Lightweight for easy handling Superior corrosion resistance • Thermally efficient