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Sprinkler Layout Calculator – Fire Sprinkler Spacing & Coverage (NBC / IS 15105)

Free fire sprinkler layout calculator: head spacing, coverage area and count per NBC 2016 / IS 15105 / NFPA 13 hazard class. No sign-up.

📐 Standard: NBC 2016 Part 4 / IS 15105
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Sprinkler Layout Calculator Calculator
Reference: NBC 2016 Part 4 / IS 15105
💧 Fire Fighting
Free fire sprinkler layout calculator: head spacing, coverage area and count per NBC 2016 / IS 15105 / NFPA 13 hazard class. No sign-up.
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ℹ️ About This Calculator

Sprinkler system layout determines the number, spacing, and arrangement of sprinkler heads to achieve complete coverage of the protected area. Correct spacing ensures each head covers its design area at the required density. This calculator determines head spacing and count based on hazard classification, ceiling height, and room geometry per NBC 2016 Part 4 and IS 15105.

IS 15105 (Design and Installation of Fixed Automatic Sprinkler Fire Extinguishing Systems) and NBC 2016 Part 4 are the primary standards for sprinkler systems in India. Hazard classes: Light Hazard (LH) – hotels, offices, hospitals, schools; Ordinary Hazard (OH1/OH2) – manufacturing, warehouses; High Hazard (HH) – flammable liquid storage, paint shops. Sprinkler heads must be within 150 mm of ceiling; sidewall sprinklers used near walls/obstructions. TAC (Tariff Advisory Committee) approval required for insured buildings.

📐 Sprinkler Layout Calculations

NBC 2016 Part 4 / IS 15105

Max Coverage per Head (A_head):
  Light Hazard (LH): 21 m² max
  Ordinary Hazard (OH): 12 m² max (open head) / 14 m² (closed head)
  High Hazard (HH): 9 m² max

Max Spacing (S):
  S_max = √(A_head) for square layout
  S_max_wall = S_max / 2 (distance from wall to first head)

Number of Heads:
  N_row = CEILING(L / S_max)
  N_col = CEILING(W / S_max)
  Total heads = N_row × N_col

Design Density (mm/min):
  LH: 2.25 mm/min; OH1: 5.0; OH2: 5.0–7.5; HH: 7.5–17.5

🧮 Worked Example

A Light Hazard office floor measuring 20 m × 12 m (240 m²) uses the standard 21 m² maximum coverage per head. Maximum spacing S_max = √21 ≈ 4.58 m, with the first head set at half that distance (≈2.29 m) from each wall.

Heads needed: N_row = CEILING(20/4.58) = 5, N_col = CEILING(12/4.58) = 3, giving 15 sprinkler heads in a 5 × 3 grid, each discharging at the Light Hazard design density of 2.25 mm/min across its design area.

📊 Sprinkler Spacing by Hazard Class (NBC 2016 / IS 15105)

Sprinkler spacing and coverage are set by the occupancy hazard class. Higher hazards demand closer heads, smaller coverage per head and greater discharge density. The values below follow NBC 2016 Part 4 and IS 15105, which align with NFPA 13.

Coverage & Spacing Limits

Hazard classMax area/head (m²)Max spacing (m)Density (mm/min)
Light hazard20.94.62.25 – 4.1
Ordinary hazard I-II12.14.64.1 – 6.1
Extra hazard9.33.78.1 – 12.2

Layout Notes

Heads must also sit within half the maximum spacing from walls, and no more than the listed distance apart along and between branch lines. Light-hazard covers offices, schools and hospitals; ordinary hazard covers most commercial and light-industrial occupancies; extra hazard covers high-fuel processes and storage. Confirm the hazard class before fixing the grid, as it drives both the head count and the pump duty.

Indicative limits - the authority having jurisdiction and the specific NBC / IS 15105 / NFPA 13 edition govern the final design.

NFPA 13 Coverage in US Units (ft²)

Hazard classMax area/head (ft²)Max spacing (ft)Max to wall (ft)
Light hazard225157.5
Ordinary hazard130157.5
Extra hazard100126
Extended-coverage (light)up to 400per listing—

Deflector & Obstruction Rules

Standard spray heads sit 25–150 mm (1–12") below the ceiling, and the “three-times / 18-inch” rule applies: keep any continuous obstruction (beams, ducts, light fittings) at a horizontal distance of at least three times its own depth from the head, and maintain a clear 450 mm (18") below each deflector so the spray develops. A head closer than this needs relocating or an additional head beneath the obstruction.

❓ Frequently Asked Questions

What is the maximum sprinkler head spacing allowed? +
Per IS 15105: Light Hazard – max 4.6 m between heads, max coverage 21 m²; Ordinary Hazard – max 4.0 m (open head), 3.75 m (closed head), coverage 12–14 m²; High Hazard – max 3.0 m, coverage 9 m². Distance from wall to first head: half the maximum spacing (e.g., 2.3 m for LH). These limits ensure full coverage with spray overlap.
What is the difference between closed and open head sprinkler systems? +
Closed head (wet/dry): Each head activates individually when its fusible element or glass bulb melts at the fire. Only heads in the fire area operate – minimising water damage. Wet pipe (always water-filled) and dry pipe (air/nitrogen-filled for freezing environments) are the two types. Open head (deluge): All heads in a zone operate simultaneously when system triggers. Used for high-hazard areas, aircraft hangars, stage areas.
Does every building in India require a sprinkler system? +
NBC 2016 mandates sprinklers for: all buildings above 15 m (5 storeys); basements over 200 m²; storage buildings over 500 m²; assembly occupancies over 1000 m²; educational over 1500 m²; high-rise buildings (above 30 m – mandatory full building coverage); special hazard areas (fuel stores, paint shops) regardless of building height. Many fire insurance providers (TAC) also require sprinklers for insured buildings.
What is a concealed sprinkler and when is it used? +
Concealed sprinklers have a decorative cover plate that pops off when the ambient temperature rises. The head is recessed into the ceiling, making it invisible in normal conditions. Used in hotels, hospitals, and high-end offices for aesthetic reasons. They are slightly slower to activate than conventional pendent heads (cover plate must detach first). Same coverage and spacing rules apply.
How do I determine the hazard class for my building? +
Light Hazard (LH): hotels, offices, schools, hospitals, residential. Ordinary Hazard Group 1 (OH1): car parks, light industrial, paper mills (low-intensity). Ordinary Hazard Group 2 (OH2): chemical works, textile mills, wood working. High Hazard (HH): flammable liquid storage, aircraft hangars, paint manufacturing. When in doubt, use the higher (more conservative) classification. TAC guidelines also provide occupancy-specific classifications.
What is the maximum sprinkler spacing for each hazard class? +
For light and ordinary hazard occupancies the maximum spacing is about 4.6 m (15 ft) between heads, reducing to 3.7 m (12 ft) for extra hazard. Heads must also be within half that distance from walls. Closer spacing may be needed to meet the required discharge density.
How much area does one sprinkler cover? +
Maximum coverage is about 20.9 m² per head for light hazard, 12.1 m² for ordinary hazard and 9.3 m² for extra hazard. Divide the protected floor area by the coverage limit to get the minimum number of heads, then arrange them within the spacing limits.
Does Indian sprinkler design follow NBC or NFPA? +
Indian design follows NBC 2016 Part 4 and IS 15105, which are closely aligned with NFPA 13. The hazard classes, coverage areas and spacing limits are broadly the same; local fire authorities and the specific standard edition determine the binding requirements.

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