When it comes time to re-roof a facility, consider a number of objectives. Most important, as the first line of defense against the elements, it should be weather-tight. But it also should be thermally efficient, economical, attractive, and offer design flexibility and long life with minimal maintenance.
One system that can effectively meet all these goals is the metal standing-seam roof. Its versatility and low life-cycle costs have made it a fast-growing roofing choice among school systems.
Standing-seam systems prevent leaks. Their design eliminates most through-the-roof fasteners, a frequent source of penetration problems. And because the roof panels are mounted on a system of concealed sliding clips, they move with thermal expansion and contraction forces rather than being pulled apart by them.
The panels interlock mechanically at standing seams, above the roof plane and away from water or ice. One available seam configuration, for example, is a full 360-degree rolled seam, designed for maximum resistance to penetration.
Standing-seam roofs normally are installed to create a minimum slope of 1/14:12. This creates positive drainage, which eliminates standing water. The slope directs water away from the building rather than channeling it to an internal system. Over time, the internal method of drainage may increase maintenance costs and provide a shorter life to the watertight integrity of the building.
Even in retrofitting flat built-up roofs that are common on older buildings, you can create this slope economically by installing a light-gauge substructural system.
Installing the replacement roof on a substructural system allows the new roof to be mounted right over the old one. This not only avoids disruption to activities inside the building and eliminates exposing the building's interior to the elements, but it also saves the labor and costs involved in removing the old roof.
Before you have a new roof designed, you should have a structural engineer inspect the building. This will determine whether the structure is adequate for the new roofing load, and, if not, what can be done to reinforce it. The inspection also will determine if the existing roof has extensive entrapped moisture-as in some failed built-up systems-and what needs to be done to provide proper ventilation.
Metal standing-seam roofs are thermally efficient and suitable for nearly any climate condition. Installing a standing-seam system over an existing roof usually creates "attic space" for adding insulation. The result is greater heating and cooling efficiency. Annual fuel savings of 20 to 30 percent are typical-and savings of as much as 75 percent have been reported in northern regions.