Metal Roofing: Frequently Asked Questions

Q. Why should I choose standing seam metal roofing?

A. The standing seam metal roof is one of the most exciting breakthroughs in roofing technology in the last 25 years. It fulfills the building owner's need for durable, puncture-resistant protection against the weather while working in concert with the forces of nature.

Metal roofing has an established track record in new construction, where it has been used in some 50 percent of all low-rise commercial and industrial buildings erected in the last several years. This acceptance has carried over to the re-roofing market, where standing seam metal roofs have been used successfully as a replacement for built-up and single-ply systems. Leading applications for standing seam metal roofs in the retrofit market are schools, factories, warehouses, distribution centers and military facilities. 

Q. What are the benefits of metal roofing?

A. Standing seam metal roofs have many benefits. A few examples follow. Metal roofs are:

Durable. The standing seam roof handles thermal shock through its concealed, sliding clip system. The clip assembly uses a rigid base attached to the building's structural members. An upper part clips the roof panel and forms into a seam during the seaming operation. The clip allows equal amounts of movement in either direction.

Lightweight. Metal roof panels weigh a relatively modest 1-1/2 pounds per square foot.

Easy to Install. Metal roofs can be installed year-round. Heavy rain, extreme cold weather or high winds are about the only conditions that prevent metal roof installers from working. In most projects, the metal roof can be installed right over the existing roof, eliminating costly and time-consuming tear-offs. Owners do not need to close the building area being re-roofed if the work must be done while occupants are inside. Occupants can continue their normal activities, even in the immediate area being re-roofed.

Easy to Maintain. Unlike flat built-up roofs that require frequent maintenance, standing seam metal roofs offer 20 years and beyond of trouble-free performance with little or no maintenance time or expense.

Weathertight. The standing seam metal roof is designed to withstand rain, wind and snow, and still remain weathertight. Panels are joined together by a weathertight seam that is raised above the roof's drainage plane. Factory-applied organic sealants are applied to the seam during roll forming of the panel. Once on site, automatic field seaming machines complete the seal.

Metal panels are attached to the roof substructure with concealed clips. These are roll formed or crimped into the panel seams without penetrating the corrosion-resistant steel weathering membrane. The clip system performs two functions: It retains the panels in position without exposed fasteners, and allows the roof to expand and contract during temperature changes.

Standing seam metal roofs are designed to perform in high-wind conditions and can qualify for a UL 580 wind uplift rating, as well as the ASTM E-1592 wind uplift test. Metal roofs also can carry a Factory Mutual Class A fire rating—the highest in the industry—which can substantially reduce insurance rates.

Reliable. Standing seam metal roofs assure adequate drainage from rain and snow, effectively solving ponded water problems, leaks and other related troubles commonly associated with flat built-up roofs. In retrofit projects, a sub-framing system is attached to the existing roof surface to provide a minimum 1/4:12 pitch for the new metal roof. 

The panel fastening system is uniquely designed to handle potentially damaging effects from thermal movement. Precisely formed, factory-made metal panels are locked in place by clips inside a raised seam standing two to three inches above the roof surface. The clips have a moveable feature that allows panels to expand and contract with temperature changes. The concealed clip system reduces the chances of leaks and makes the standing seam roof attractive.

Q. Are metal roofs energy-efficient?

A. Yes. Fiberglass blankets are the most common insulation material in standing seam metal re-roofing projects. On some projects, unfaced fiberglass insulation is simply laid directly on the existing roof surface before insulation blankets of the new standing seam roof. For other projects, insulation blankets are installed directly under the metal panels and stretched over supporting members. Foam insulation blocks are often used to separate the panels from the purlins to prevent thermal short-circuiting and condensation from forming. The roof expands and contracts independent of the insulation, giving the roof surface a floating action.

Q. Are standing seam metal roofs cost-effective?

A.  Standing steam metal roofs pay for themselves from the day that they are installed. And, they are cost-competitive.

Twenty-year material warranties are customary for metal roofing systems, which is considerably longer than the standard protection for built-up and single-ply systems. Long-term warranties are sometimes offered for weathertightness on metal roofs, including those with a 1/4:12 slope. 

Standing seam metal roofs can qualify for the UL-90 wind-uplift rating—the highest in the industry—that can substantially reduce insurance rates in high-wind areas. It must be combined with the roof manufacturer's UL-90 system, which includes the panels, concealed clips, sealants and structural supports. The standing seam metal roof can also carry a Factory Mutual Class A fire rating.

Q. Do standing seam metal roofs resist corrosion?

A. Metal roof panels resist corrosion with the help of a zinc, aluminum, or aluminum-zinc alloy metallic coating applied to the base steel.

Additional protection can come from attractive, specially pigmented organic paints that harmonize the roof with conventional brick, concrete and wood sidewall materials. Popular beige and earth-tone colors allow architects to coordinate the roof attractively with other design elements of the building.

Q. I need a material that has flexibility in design. Should I consider standing seam metal roofing?

A. Yes. Steep slopes and flat roof profiles can be designed with the standing seam roof. The structural roof is the industry's alternative to flat built-up and single-ply systems. The roof spans from support structural to support structural in new construction with slopes of 1/4:12 or more. The architectural standing seam roof is used for visually exposed roofs, mansards facia, and similar applications. It is a water shedder and needs slopes of 3:12 or greater.

Like wood shakes, tile and slate, this application needs some form of decking for support and a base felt for added protection against moisture penetration.

Q. Are standing seam metal roofs recyclable?

A. Yes. The overall recycling rate of steel products in North America is 83.3 percent (2008 data from the Steel Recycling Institute, the most recent available)—the highest of any construction material. Building professionals are becoming increasingly aware of the importance of using recyclable metal roofing materials for retrofit applications over old non-metallic roofs. This helps avoid expensive tear-off and disposal of solvent and chemical-based materials, which often wind up in overburdened landfills.

Q. Should I consider standing seam metal roofing for retrofit projects?

A. In most retrofit projects, standing seam metal roofs can be installed right over existing built-up roofs, eliminating costly and time-consuming tear-offs. The metal panels are attached to a steel sub-assembly to provide the necessary slope for ice and water to drain, providing a low-slope solution to flat built-up roofs.