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Sprinkler obstructions: three-times rule and beams
For standard spray upright or pendent sprinklers. Enter the obstruction width and the distance from the sprinkler to the side of the beam.
Quick answer
A 150 mm obstruction needs the sprinkler at least 450 mm away. At 600 mm from the beam side the deflector may be at most 140 mm above the beam bottom.
Preliminary results
Minimum distance to obstruction450mm
Max deflector height above beam bottom140mm
| Step | Result | Basis |
|---|---|---|
| Three-times rulemin(3 × 150; 610) | 450 mm | NFPA 13 ⚠ |
| Beam table600 mm | 140 mm | NFPA 13 ⚠ |
Sources and assumptions. NFPA 13: three-times rule (distance ≥ 3 × obstruction width, no more than 610 mm / 24 in required) and beam rule table for standard upright/pendent sprinklers ⚠. Converted from inches, rounded. ⚠ = code table value to be checked against the original standard. Preliminary results for material selection and budgeting; not a substitute for an approved fire protection design.
Distance to beams
| Distance to side of beam | Max deflector height above beam bottom |
|---|---|
| < 300 mm | 0 mm |
| 300–450 mm | 64 mm |
| 450–600 mm | 89 mm |
| 600–750 mm | 140 mm |
| 750–900 mm | 191 mm |
| 900–1050 mm | 241 mm |
| 1050–1200 mm | 305 mm |
| 1200–1350 mm | 356 mm |
| 1350–1500 mm | 419 mm |
| 1500–1650 mm | 457 mm |
| 1650–1800 mm | 508 mm |
Frequently asked questions
What is the three-times rule?
A sprinkler must be at least three times the obstruction width away so the spray can wrap around it. A 100 mm pipe needs 300 mm. No more than 610 mm is required.
How close can a sprinkler be to a beam?
The closer to the beam, the lower the deflector must be. Within 300 mm of the beam side the deflector cannot be above the beam bottom.