| Primary value | 12 m² ((typical Light Hazard)) |
| Applies to | Wet pipe sprinkler systems in buildings |
| Exceptions | Light Hazard (residential, office) → 12 m² (max 4.6 m spacing) |
| Ordinary Hazard Group I → 12 m² (max 4.0 m spacing) | |
| Ordinary Hazard Group II → 9 m² (max 4.0 m spacing) | |
| Extra Hazard → 9 m² (max 3.7 m spacing) | |
| Sprinkler Type → Values cited are for Standard Spray Sprinklers (Upright/Pendent). Extended Coverage (EC), Sidewall, and ESFR sprinklers have different, specific rules. | |
| High-Piled Storage → Warehouses with high-piled storage require special design, often using ESFR sprinklers or in-rack sprinklers, with different spacing and density requirements per IS 15105. | |
| Obstructions → Clearance from obstructions like beams, columns, and ducts is critical and governed by specific rules in IS 15105 to ensure proper spray pattern development. | |
| Sloped Ceilings/Roofs → For sloped surfaces, the horizontal distance is used for spacing, and total coverage area per sprinkler must be adjusted based on the slope. | |
| Measured as | Plan area covered by a single sprinkler head. Spacing between heads must be checked against both lengthways and crossways limits. |
| Source | NBC 2016 — IS 15105:2021, Clause 11, Tables 10 & 11 ✓ Verified |
Ensuring complete coverage as per IS 15105 is a mandatory life-safety requirement for specified building types in India. Incorrect spacing can lead to fire spread between sprinkler heads, rendering the system ineffective and failing to meet statutory approval from the local Fire Authority.
Engineers identify the hydraulically most remote 'Area of Operation' as defined in IS 15105 for the specific hazard class (e.g., 84 m² for Light Hazard). Hydraulic calculations for this area determine the required flow and pressure, which in turn sizes the fire pump and main piping.