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.