This part of the web site contains general specification information for GALVALUME standing seam roofs. Please contact a manufacturer of GALVALUME standing seam roofs for more detailed specification information. You can locate a manufacturer by selecting the "Where to Buy" link in the tool bar located on the right hand part of this screen.
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.
Applicable Standards: GALVALUME sheet is produced according to ASTM Specification A792/A792M-97a "Steel Sheet, 55% Aluminum-Zinc Alloy-Coated by the Hot-Dip Process." It is supplied in commercial, lock-forming and structural qualities. Each grade is available in AZ50 (AZ150-metric), AZ55 (AZ165-metric), and AZ60 (AZ180-metric), coating weights. AZ50 or 0.50 oz/sq. ft. (150 g/sq. m.) coated GALVALUME sheet is generally used for prepainted architectural GALVALUME SSR and AZ55 or 0.55 oz/sq. ft. (165 g/sq. m.) for unpainted structural GALVALUME SSR.
GALVALUME structural SSR roof systems are generally fabricated and installed to meet the UL-90 rated wind up-lift resistance requirement specified in the Underwriters Laboratories' UL 580 test. However, these systems must be installed exactly as tested because performance is dictated by sheet thickness and width, clips, fasteners, secondary structural gages and spacings, as well as by panel rib height and configuration.
Many GALVALUME SSR manufacturers offer roof systems which have wind uplift capability established in accordance with the recently published ASTM Specification E1592, "Test Method for Structural Performance of Sheet Metal Roof and Siding Systems by Uniform Static Air Pressure Difference".
Bare and prepainted GALVALUME sheet have also been incorporated guide specifications for metal building systems and components by the U.S. Army Corps of Engineers. Some typical specifications are: CEGS-07413, "Metal Roofing and Siding Plain"; CEGS-07415, "Metal Roofing and Siding, Factory Color Finish"; CEGS-07416, "Metal Buildings"; and CEGS-13120, "Standing Seam Metal Roof System." The Department of Navy also recognizes prepainted GALVALUME sheet in guide specification NFGS-13121.
The paint coatings on GALVALUME SSR panels are tested in accordance with the following ASTM specifications. Performance requirements vary with the type of paint. GALVALUME SSR panel manufacturers should be consulted for specific data.
- Color change and chalk- ASTM D2244, "Method for Calculation of Color Differences and Instrumentally Measured Color Coordinates"; and D659, "Method of Evaluating Degree of Chalking of Exterior Paints"
- Adhesion- ASTM D2795, "Test Method for Resistance of Organic Coatings to the Effects of Rapid Deformation(Impact)"; D3359, "Test Methods for Measuring Adhesion By Tape Test"; and D4145, "Standard Test Method for Coating Flexibility of Prepainted Sheet"
- Coating hardness- ASTM D3363 "Test Method for Film Hardness By Pencil Test"
- Formability- ASTM D3281, "Test Method for Formability of Attached Organic Coatings with Impact-Wedge Bend Apparatus"
- Gloss Retention- D523, "Test Method for Specular Gloss"
- Humidity- ASTM D2247,"Practice for Testing Water Resistance of Coating in 100% Relative Humidity"; and D4585, "Standard Practice for Testing Water Resistance of Coatings Using Controlled Condensation"
Because a GALVALUME SSR is noncombustible, it can be incorporated in systems which meet favorable Factory Mutual and Underwriter Laboratories fire classifications. Such a classification can result in lower insurance costs.
Atmospheric Corrosion Resistance:
Based on 30-year atmospheric corrosion R&D tests, it is estimated that GALVALUME sheet will outlast G90 galvanized by two to four times in marine, industrial and rural atmospheres. GALVALUME panels are still rust-free after 30 years in all but the severe marine environment. The estimated life of the 55% Al-Zn coating (years to first rust) based on these 30-years tests ranges from 14 years to 40 or more years.
A survey of 82 unpainted GALVALUME low slope (1:12 slope or less) roofs up to 22 years old in the Eastern-half of the U.S. reconfirms the prediction from the R&D tests that GALVALUME roofs will last 30+ years. The GALVALUME steel roofs are in excellent condition and easily meet their 20-year performance warranty. After 20+ years the 55% Al-Zn coating is intact and protecting the steel substrate from corrosion. Based on their appearance, most roofs should last 30 to 40 years, before requiring major maintenance, such as field painting.
Prepainted GALVALUME sheet has also exhibited excellent corrosion resistance in a variety of accelerated tests and atmospheric exposures and on buildings. It has demonstrated equal or better performance than prepainted G90 galvanized in corrosion at flat areas, paint damaged areas, formed areas and roof drip edges.
Typical Mechanical Properties:
GALVALUME sheet used for SSR panels has the following range of mechanical properties:
- Yield Strength: 40-60 ksi (276-414 MPa)
- Tensile Strength: 55-70 ksi (379-483 MPa)
- Total Elongation: 18-36%
- Hardness: 50-65 HRB
Structural quality grades, including 50 ksi (345 Mpa) and 80 ksi (552 Mpa) minimum yield strengths are also available. Mechanical property requirements are covered in ASTM Specification A792/A 792M.
Engineering data such as section properties and load values for specific SSR panel profiles are available from GALVALUME SSR panel manufacturers.
Because of their light weight, retro-fit GALVALUME SSR systems can be installed over most existing non- metallic roofs, thereby eliminating the cost of tear-offs and disposal and non-metallic roofing materials, while reducing the burden on landfills. Removal and disposal of hazardous asbestos roof panels on old industrial, government and military buildings can also be avoided by installing retro-fit GALVALUME SSR systems directly on such roofs. Elimination of tear-offs also avoids exposing the interior of the building to weather and disrupting activities taking place within buildings.
Because of the wide variety of panel profiles and design features, GALVALUME SSR systems should be installed according to SSR panel manufacturers' construction practices and details. SMACNA (Sheet Metal and Air Conditioning Contractors National Association) Architectural Sheet Metal Manual specifications should be used as a guide and basis for details wherever applicable.
Structural GALVALUME SSR systems are typically installed directly on purlins on new roofs. Concealed clips are attached to the purlins and the GALVALUME SSR panels and clips are joined together by forming, crimping or snapping at the seams. Clips are designed with slots and tabs to accommodate thermal expansion and contraction.
Fiberglass blanket insulation is most commonly used on new structural GALVALUME SSR systems to reduce energy costs and to provide noise dampening. The insulation blankets are installed directly under the panels and stretched over the supporting structural members. The underside (towards the inside of the building) of the insulation typically has a vapor retarder to prevent moisture penetration from inside the building and subsequent water condensation on the underside of the SSR panels. Vapor retarder closure systems and seams must be sealed correctly and all punctures, penetrations or holes in the vapor retarder must be repaired with tape. Foam insulation blocks are also generally used to separate the panels from the purlins to prevent thermal short circuiting.
Compatible accessories, flashings and gutters are available for structural GALVALUME SSR systems. Large equipment units are mounted on curbs which expand and contract with the roof and small openings are accommodated with flexible roof jacks. Gable, eave and parapet wall flashings are also used to lock out water and moisture. Other special components include walkways, ventilators, scuttles and gutters.
For retro-fit applications, structural GALVALUME SSR is installed on a sub-framing system which, in turn, is attached to the existing roof surface to provide a minimum 1/4:12 slope for the new roof. The structural members of most existing non-metallic roofs can support the lightweight SSR panels and structural steel sub-framing system, which weigh about 2 to 5 lbs/sq.ft. (9.8 to 24.4 kg/sq. m.). However, the existing roof structure should be analyzed to determine that it can support the anticipated loads. Insulation blankets can be installed on the sub-framing system the same as on new roofs or simply laid directly on the existing non-metallic roof surface. Ventilation of the cavity between the new roof and the old roof should be considered to avoid condensation. SSR panel manufacturers should be consulted for design and installation details of the sub-framing system for retro-fit applications.
Architectural GALVALUME SSR systems are typically installed on a metal or wood deck fastened to the roof structural system. Concealed clips are used to fix the panels to the deck. Spacing of clips and the number of fasteners per clip are specified by the SSR panel manufacturer. A layer of 30 pound felt paper, or equivalent, should be used to insulate the deck from the GALVALUME SSR panel. An insulation/waterproofing underlayment is particularly important when installing a GALVALUME SSR system on chemically treated wood deck.
Because architectural panels are used for aesthetic purposes, care should be exercised in handling and installing such panels. Painted panels need to be protected from damage. Scratching of the paint can be caused by walking on the panels or using improper tools during installation. Some manufacturers supply painted panels with a strippable clear plastic film to protect the surface during installation. Such films should be removed within one week after the panels are installed.
Unpainted GALVALUME architectural SSR panels should also be handled carefully during installation.
Gloves should be sued to avoid hand marking and foot traffic should be avoided to eliminate shoe scuffing and marking. Panel manufacturers should be consulted when unpainted GALVALUME SSR architectural panels are to be used. Careful handling of such panels is required from manufacture to installation.
Other design, installation and maintenance guidelines for GALVALUME SSR systems are:
Standing water conditions should be avoided by providing for drainage of water from roofing panels and around roof penetrations. SSR panel manufacturers can provide installation details.
Cascading water from higher roof elevations onto lower roof panels can cause erosion of the paint and metal coating on GALVALUME SSR. Panel manufacturers should be consulted for handling expected large volumes of rainwater draining from GALVALUME SSR.
Snow and Ice:
Special design considerations are required in heavy snow areas to accommodate additional snow loads, sliding snow off the roof and ice damming at eaves. Design guidelines for the roof system should be discussed with SSR panel manufacturers.
Copper, lead and unprotected steel should not be used with GALVALUME SSR panels. Likewise, GALVALUME SSR panels should not come in direct contact with wet and/or weather treated wood or uncured concrete. Wood retains moisture and weather treatments contain corrosive chemicals that can shorten the life of a panel in direct contact. Uncured concrete is very alkaline and may attack the aluminum-zinc coating. Compatible, long-life flashing such as GALVALUME and aluminum sheet should be used.
Compatible fasteners with long-term corrosion resistance should be used for GALVALUME SSR systems. Recommendations for suitable fasteners are available from panel and fastener manufacturers.
Good quality sealants should be used that provide long- term resiliency and flexibility necessary to seal the joints for the life of the GALVALUME SSR panel. Sealants with acetic acid should be avoided. Contact SSR panel or sealant manufacturers for specific recommendations.
Air Conditioner Drains:
Drain water from air conditioners contains dissolved copper from the condensation coils. Discharge of this drain water from roof-top units onto GALVALUME SSR panels can cause rapid corrosion of the aluminum-zinc coating. Condensate from air conditioners should be discharged through a plastic pipe extended at least to the rain gutter but preferable to the ground.
After erection, GALVALUME SSR panels should be swept to remove dirt and debris such as unused fasteners, metal filings and drillings, pop-rivet stems and pieces of flashing. For example, metal drillings can rust quickly and easily be mistaken for rusting of the GALVALUME sheet.
A structural GALVALUME SSR system is a low cost alternative to non-metallic roofs, particularly when considering life-cycle costs. Because of its lighter weight, a GALVALUME SSR system also lowers the structural support requirements in new construction. Likewise, for retro-fit projects, structural GALVALUME SSR systems can usually be installed directly over the old roof, eliminating the need for tear-off. This saves labor and disposal costs, and avoids disrupting activities inside the building. GALVALUME SSR systems can also be installed year-round.
Compared to various types of low slope non-metallic roof systems, a structural GALVALUME SSR is projected to have the lowest life cycle cost. For example, over a 40-year period, non-metallic roof system for schools in Alabama are expected to cost two to four times more than a structural GALVALUME SSR. (See Table). For specific costs of structural and architectural GALVALUME SSR systems, contact panel manufacturers.
Projected 40 Year Roof Cost — Tuscaloosa School System, Tuscaloosa, AL
|Material||Installed Cost||Total Maintenance||40 Year Total Roof Cost|
|SSR||$5.05 sq/ft||$0.69 sq/ft||$5.74 sq/ft|
Both a 20-year material performance and a roof weather-tightness warranty are available for GALVALUME SSR systems. Paint systems warranties also exist for color, fade, chalking and film integrity. GALVALUME SSR panel and paint manufacturers issue such warranties upon request for a designated building. Depending on the type and scope of the warranty, an extra charge may be required. GALVALUME SSR panel and paint manufacturers should be contacted for details.
Minimal maintenance of GALVALUME SSR panels is required. The roof should be inspected at least once a year. Debris such as leaves, branches and trash should be removed from gutters, at ridge caps and in corners. Roof top ancillaries and air conditioner supports, drains and housings should be checked. Particular attention should be paid to installation practices used for add- on roof ancillaries that create new roof penetrations. Any exposed metal that can rust or has rusted should be painted.
Technical services are available from SSR panel manufacturers, paint manufacturers and GALVALUME sheet steel producers. They all have regional manufacturing, distribution and sales offices located throughout North America. Additional product information is available from GALVALUME SSR panel manufacturers and the GALVALUME Sheet Producers of North America upon request.