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IS 15965:2012 is the Indian Standard (BIS) for coated steel sheets for roofing and cladding. This standard specifies the requirements for steel sheets intended for roofing, cladding, and related applications. It covers both metallic coated (like galvanized or zinc-aluminium alloy) and pre-painted/organic coated steel sheets, detailing material properties, dimensional tolerances, coating characteristics, and performance test methods.
Specifies requirements for pre-coated and pre-painted metallic coated steel sheets/coils for roofing and cladding.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Differentiate between Base Metal Thickness (BMT) and Total Coated Thickness (TCT). Structural calculations must use BMT.
! Ensure the specified coating mass (e.g., AZ150) is verified, as lower coating mass drastically reduces corrosion resistance and service life.
! Avoid using heat-generating abrasive cutters for cutting sheets on-site as it damages the protective coating, leading to premature rusting at the edges.
Covers technical requirements for coil-coated steel with organic coatings on metallic substrates.
ASTM A755 / A755M - 18ASTM International, USA
HighCurrent
Standard Specification for Steel Sheet, Metallic Coated by the Hot-Dip Process and Prepainted by the Coil-Coating Process for Exterior Exposed Building Products
Specifies prepainted metallic-coated steel sheet for exterior building products, a direct parallel.
AS/NZS 2728:2013Standards Australia / Standards New Zealand
MediumCurrent
Prefinished/prepainted sheet metal products for interior/exterior building applications — Performance requirements
Focuses on performance requirements of the finished product, less on substrate manufacturing details.
JIS G 3322:2019JSA (Japanese Standards Association), Japan
MediumCurrent
Prepainted hot-dip 55% aluminium-zinc alloy-coated steel sheet and strip
Specific to prepainted Al-Zn coated steel, one of the types covered by IS 15965.
Key Differences
≠IS 15965 specifies base steel grades by yield strength (e.g., 240, 340, 550 MPa) referencing Indian Standards, whereas EN 10169 uses grades like S250GD, S350GD, and ASTM A755 uses grades like SS 33, SS 50, SS 80 (in ksi).
≠The minimum specified metallic coating mass differs. A common grade in IS 15965 is Z120 (120 g/m² zinc), which is lower than the common minimum G60 (180 g/m²) or G90 (275 g/m²) often required by building codes referencing ASTM A755.
≠UV resistance and weathering requirements vary. EN 10169 has defined categories (Ruv1-Ruv4) and AS/NZS 2728 has very stringent long-term outdoor exposure test requirements for certain durability classes, which are more extensive than the 1000-hour accelerated QUV test in IS 15965.
≠IS 15965 provides specific coating thickness ranges for different paint systems (RMP, SMP, PVDF). ASTM A755 is less prescriptive on nominal thickness, focusing more on performance outcomes and allowing it to be an agreement between supplier and purchaser.
Key Similarities
≈All standards cover continuously coil-coated (prepainted) steel sheets intended for exterior building applications such as roofing, cladding, and walling.
≈They all recognize and specify requirements for the two primary metallic substrates: hot-dip zinc (galvanized) and hot-dip aluminium-zinc alloy coated steel.
≈A core suite of performance tests for the organic coating is mandated across all standards, including flexibility (T-bend), adhesion (cross-hatch/grid), impact resistance, and corrosion resistance (salt spray).
≈All standards include clauses that specify permissible dimensional and shape tolerances for thickness, width, length, camber, and flatness to ensure product consistency.
Parameter Comparison
Parameter
IS Value
International
Source
Base Metal Yield Strength (High Strength)
550 MPa minimum
S550GD (550 MPa minimum)
EN 10346 (referenced by EN 10169)
Al-Zn Coating Mass (Common Grade)
AZ150 (150 g/m² min total)
AZ50 (150 g/m² min total)
ASTM A792/A792M
Zinc Coating Mass (Common Grade)
Z120 (120 g/m² min total)
Z275 (275 g/m² min total) / G90 (US equivalent)
EN 10346 / ASTM A653M
Top Side Organic Coating Thickness (Typical)
18 - 25 µm (depending on paint system)
25 µm (nominal for standard polyester)
EN 10169:2022
Flexibility (T-Bend Test, typical)
≤ 4T (No cracking under 7x magnification)
≤ 6T (No paint pick-off)
ASTM A755 / A755M - 18
Salt Spray Test Duration (Standard)
1000 hours
Up to 1440 hours (for highest corrosion category RC5)
EN 10169:2022
Pencil Hardness
H minimum
F minimum (often specified, but can vary by paint system)
ASTM A755 / A755M - 18
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Minimum Yield Strength for High Strength Grade550 MPa
Standard Metallic Coating Mass (Zinc-Aluminium)150 g/m² (AZ150)
Standard Metallic Coating Mass (Zinc)275 g/m² (Z275)
Nominal Top Coat Paint Thickness (Exterior)20 microns
T-Bend Test requirement for flexibility≤ 6T
Tables & Referenced Sections
Key Tables
Table 1 - Tolerances on Thickness, Width and Length
BMT (Base Metal Thickness) is the thickness of the steel core. TCT (Total Coated Thickness) includes the steel, metallic coating, and paint layers. Structural strength depends on BMT (Clause 5.1).
What does AZ150 mean?+
It denotes a zinc-aluminium alloy coating with a minimum total mass of 150 grams per square meter on both surfaces, as specified in Table 3.
What is the common high-strength grade for roofing sheets?+
Grade 550, which has a minimum yield strength of 550 MPa, is commonly used for high-strength roofing and cladding profiles (Table 2).
What is the T-bend test?+
It's a test to check the flexibility and adhesion of the paint coating by bending a sample. The 'T' value indicates the number of sheet thicknesses used as the bending radius (Clause 6.2).