GALVALUME Standing Seam Roof (SSR) systems are made up of metallic coated steel sheet panels joined together at their sides with seams and fastened to the roof substructure with concealed fasteners and/or clips. GALVALUME SSR system can be used for both structural and architectural roofs. Panels can be painted or can remain unpainted. Roofs can be used on buildings as replacement or retrofit roofs on old buildings.
Structural GALVALUME SSR is generally applied directly to the purlin/joist roof substructure. It is typically near-flat with a minimum slope of 1/4:12. This minimum slope is sufficient for draining water off the roof. Panel seams range from 2 to 3 in. (51 to 76 mm) above the roof drainage surface depending on the roof panel profile. Panel corrugation profiles can be flat or trapezoidal and panels range from 10 to 30 in. (250 to 760 mm) wide. Panels can be factory formed and delivered in lengths usually limited up to 45 ft. (14m.) because of highway transportation restrictions.
They can also be job-site formed with portable roll formers in lengths up to 200 ft. (61 m.). Panels are interlocked together along longitudinal seams above the panel flats. Depending on the design of the panel, joining is done by field seaming with a portable lockforming machine, by "T" seams held together with a cap strip crimped to the seam with a portable crimping machine or a snap-together seam.
A sealant is normally applied to the seam during roll forming of the panel to ensure a water-tight joint. Panels are attached to the roof substructure with concealed clips. These clips are roll formed or crimped into the panel seams without penetrating the steel weathering membrane. They are attached to the supporting purlins and some are designed to allow the roof to expand and contract during temperature changes. Seam panels are generally fixed at eaves and expansion and contraction is accommodated at the ridge.
Unpainted GALVALUME sheet is generally used for structural SSR systems. For retro-fit applications, a new roof sub-framing system is typically installed directly over the old roof. A minimum slope of 1/4:12 is incorporated in the new sub-framing system and installation of panels is as described above. Since the weight of GALVALUME SSR panels and sub-framing system ranges from about 2 to 5 lbs/ft2 (9.8 to 24.4 kg/m2), most original roof substructures can accommodate a retro-fit installation without tearing off the old roof membrane. However, an analysis of the old roof substructure should be made to confirm that it can support an in place retro-fit GALVALUME SSR system.
Insulation can be readily installed on both new and retro-fit roofs to conserve energy. Consideration should be given to ventilating the cavity between the old roof and the new roof on a retro-fit application to avoid condensation.
Architectural GALVALUME SSR systems are used in aesthetic roof applications in which form and color are important. Painted panels are normally used for these architectural applications. Roof slope is generally steep, typically 2:12 or greater. This steep slope provides for fast runoff of water. Architectural panels are usually applied to a solid deck rather than directly to the roof purlins. Decking can be wood or metal.
Thirty-pound felt paper, or equivalent, is used between the panel and deck. Some architectural GALVALUME SSR systems are designed for direct attachment to the roof substructure like that of a structural SSR system. Panel profiles are generally flat and about 10 to 24 in. (250 to 610 mm) wide. Minor longitudinal ribs may be formed in the panel for strength and form.
Architectural SSR panels are typically shorter in length than structural SSR panels. Panels can be factory formed or job-site formed. Panels are joined at longitudinal seams. Seams are generally variations of standing snap-together seams or batten seams. Batten seams can be traditional box batten or cap batten, as well as integral batten seams. Snap-together and batten seams typically range from about 3/4 in. (19 mm) about 2 in (51 mm) high.
Panels with snap-together seams or traditional batten seams are attached to the deck with concealed clips or cleats that are fastened to or fixed into the seam. Integral batten panels are fastened with clips or directly to the deck with concealed fasteners. Clips and cleats are typically designed to be movable or stationary so that thermal expansion and contraction of panels can be accommodated.
Composition and Materials
GALVALUME SSR systems are made with steel panels having a coating of corrosion resistant aluminum-zinc alloy applied by a continuous hot dip process. The nominal composition of the coating is 55% aluminum, 43.5% zinc and 1.5% silicon. GALVALUME is the trade name for this patented sheet steel product. The alloy coating of aluminum and zinc combines the best properties of both metals. It has the corrosion resistance and heat reflectivity characteristic of aluminum coatings, with the formability and galvanic protection of cut edges characteristic of zinc coatings.
GALVALUME sheet is supplied in a range of sheet thicknesses and widths and with a range of strength and ductility levels suitable for the various roofing profiles made by SSR panel manufacturers. For structural SSR applications, GALVALUME sheet is generally used unpainted. Unpainted GALVALUME sheet has a distinctive small spangled, white metallic surface.
GALVALUME sheet for architectural SSR systems is typically supplied with a baked-on paint finish. Various types of paints are applied in a wide range of colors and finished on a continuous paint line. Processing on the paint line includes cleaning, pretreating, priming, painting and baking of the paint all in one continuous process.
Two coats of paint are normally applied to both sides of the GALVALUME sheet: a corrosion inhibitive primer and a top coat. The primer is applied at a thickness specified by the paint manufacturer (typically about 0.25 mil). The top coat thickness varies depending on paint type and end use. Paint types include polyesters, silicone polyester, fluorocarbons and plastisols.
GALVALUME SSR panels are finished and ready for installation. Care must be exercised during unloading, storing and installation to avoid damage by bending, warping, twisting, scoring and corrosion. Particular care is required to avoid damaging the paint film on prepainted GALVALUME SSR panels.
GALVALUME SSR architectural panels are susceptible to "oil canning" like other light gage metal panels. Oil canning is an inherent characteristic and can be defined as a perceived waviness in flat areas of panels. Generally the period and amplitude of the wave depends on the continuous width of the flat area. Oil canning can be caused by metal coil processing, and panel fabrication and installation. Steps can be taken to minimize each of these causes. Oil canning is considered an aesthetic problem and not a reason to reject the panels. Panel manufacturers should be consulted regarding this condition.
Unpainted GALVALUME panels are occasionally used for architectural applications. In such cases, panels should be handled with clean gloves to avoid hand marking and foot traffic should be avoided to prevent shoe scuffing. SSR panel suppliers should be advised of such unpainted architectural applications and installers should request specific handling instructions.
GALVALUME SSR panels can also be damaged by corrosion if improperly stored at a job site. Panel stacks should be stored off the ground on skids under a waterproof covering. Leave space between the cover and the sheets to allow air to circulate. Skids should be positioned such that the stack of panels are on a slope so that if rain should penetrate the covering, water will drain off the panels.