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IS 2309:1989 is the Indian Standard (BIS) for protection of buildings and structures from lightning. This standard provides guidelines for the design, installation, testing, and maintenance of lightning protection systems to safeguard buildings and structures against direct lightning strokes.
Recommendations for the design, installation, and maintenance of lightning protection systems for buildings and structures, often referenced alongside newer standards.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Do not assume lightning protection is mandatory for all buildings; use the Table 1 risk assessment index to logically justify its requirement.
! The structural reinforcement steel of a building can be used as a down conductor provided electrical continuity is adequately welded and ensured.
! Earth terminations of the lightning protection system must be bonded to the main electrical earthing system of the building to prevent dangerous potential differences.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
copperaluminumgalvanized ironsteel
International Equivalents
Similar International Standards
IEC 62305 Series (Parts 1-4)IEC (International)
HighCurrent
Protection against lightning
Directly corresponds to the modern, risk-based approach for lightning protection, superseding the principles of IS 2309:1989.
NFPA 780NFPA (US)
MediumCurrent
Standard for the Installation of Lightning Protection Systems
Covers installation of LPS but uses a different risk assessment methodology and component specifications than the IEC series.
BS EN 62305 SeriesBSI (UK / Europe)
HighCurrent
Protection against lightning
The European adoption of the IEC 62305 series, making it functionally identical to the primary international standard.
IS 2309:1989 (Withdrawn)BIS (India)
HighWithdrawn
Code of practice for protection of buildings and structures from lightning
This is the original Indian standard, now superseded by the direct adoption of the IEC 62305 international standard.
Key Differences
≠IS 2309:1989 uses a prescriptive, points-based system to determine if protection is necessary. The modern equivalent, IEC 62305-2, uses a comprehensive quantitative risk management approach to determine the required Lightning Protection Level (LPL).
≠The concept of four distinct Lightning Protection Levels (LPL I, II, III, IV), which dictates all design parameters in IEC 62305, is absent in IS 2309:1989. The older code provides more generalized specifications.
≠IS 2309:1989 offers very limited guidance on protecting internal electronics. IEC 62305 has a dedicated part (Part 4) detailing the design of a coordinated Surge Protection Device (SPD) system to protect against Lightning Electromagnetic Impulse (LEMP).
≠The calculation for separation distance to prevent side-flashing is much simpler in IS 2309:1989 compared to the more detailed formula in IEC 62305-3, which accounts for the LPL, conductor length, and material insulation.
Key Similarities
≈Both standards define an external Lightning Protection System (LPS) using the same fundamental components: an air-termination system, a down-conductor system, and an earth-termination system.
≈Both codes recognize the necessity of equipotential bonding, requiring that metallic services (like water, gas pipes) entering the structure are bonded to the main earthing terminal.
≈The accepted methods for designing the air-termination system, including the use of vertical rods (Franklin method), catenary wires, and meshed conductors, are conceptually similar in both standards.
≈Both standards emphasize the critical role of a low-resistance earth termination system to safely dissipate lightning current and recommend using a combination of vertical rods and ring conductors.
Parameter Comparison
Parameter
IS Value
International
Source
Risk Assessment Method
Prescriptive points-based system to determine need for LPS.
Quantitative risk analysis to determine the required Lightning Protection Level (LPL I-IV).
IEC 62305-2
Air-Termination Design Method
Primarily uses the 'Cone of Protection' method with a 45° angle for structures up to 20m.
Primarily uses the 'Rolling Sphere Method' with radii dependent on LPL (20m for LPL I, up to 60m for LPL IV).
IEC 62305-3
Typical Down-Conductor Spacing
Maximum spacing of 30m, with additional conductors based on ground area.
Average spacing is determined by LPL: 10m (LPL I/II), 15m (LPL III), 20m (LPL IV).
IEC 62305-3
Roof Conductor Mesh Size
Recommends a grid of 10m x 20m.
Maximum mesh size is determined by LPL: 5x5m (LPL I), 10x10m (LPL II), 15x15m (LPL III), 20x20m (LPL IV).
IEC 62305-3
Minimum Earth Resistance
The combined resistance of the earthing system should ideally not exceed 10 Ohms.
A value below 10 Ohms is recommended, but the primary requirement focuses on minimum electrode length (e.g., 5m) and configuration (Type A/B).
IEC 62305-3
Min. Cross-Section (Copper Conductor)
50 mm² (e.g., 20mm x 2.5mm tape).
50 mm² (minimum thickness 2mm for tape).
IEC 62305-3
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Maximum earth resistance of lightning protection system10 Ohms
Standard spacing of down conductors20 m
Spacing of down conductors for structures >20m high10 m
Minimum cross-section for copper strip down conductor20 x 3 mm
Minimum cross-section for galvanized iron strip down conductor20 x 3 mm
Key Formulas
Risk index = A + B + C + D + E + F + G — Overall assessment of risk
Tables & Referenced Sections
Key Tables
Table 1 - Overall Assessment of Risk
Table 2 - Materials and Minimum Dimensions of Air Terminations
Table 3 - Materials and Minimum Dimensions of Down Conductors
What is the maximum permissible earth resistance for a lightning protection system?+
The resistance of the earth termination system as a whole should not exceed 10 Ohms (Clause 10.1.2).
How do you determine if a building requires lightning protection?+
By calculating the overall risk index using factors like structure use, construction type, height, and location. If the risk index is above the acceptable threshold, protection is needed (Clause 6.1.1).
Can structural steel columns be used as down conductors?+
Yes, provided the structural steel is electrically continuous from the roof to the earth termination.