Fire Watch Guards For Construction Sites
Contents
Construction Fire Watch Guard Ratio Per Sq Ft
Big pads look empty, but sawdust, plastic pipe and 55 gallon solvent drums turn a job site into a giant tinderbox. When the temporary sprinkler is off line or the panel is acting up, code requires fire watch, yet most supers guess the headcount. Guess wrong and the inspector writes a violation for every missed square foot.
The Magic Ratio
NFPA 241 and most state amendments use one simple number: one fire watch guard per 5,000 square feet of protected area. That is a hard ceiling, not a suggestion. Build a 50,000 sq ft warehouse and you need ten guards, not two guys with radios.
- 5,000 sq ft = 1 guard
- 7,500 sq ft = 2 guards (round up, never down)
- High hazard work like torching steel = ratio doubles to 2,500 sq ft per guard
- Wind above 15 mph = add one extra guard regardless of area
What Counts as Area
Include every floor that is under construction, even if the roof is open sky. Mezzanines, hoist ways and scaffolding platforms all count once they hold combustible material. Do not deduct for temporary walls; the guard must patrol the entire footprint.
High Hazard Triggers
Torch applied roofing, cutting steel deck or welding structural steel all cut the ratio in half. A 10,000 sq ft roof with torch work needs four guards, not two. The same roof with only nail guns stays at two guards.
Real World Example
A general contractor had a 45,000 sq ft tilt up building. Ordinary carpentry work, no hot work planned. He posted four guards thinking “one per corner.” The inspector measured 45,000 divided by 5,000 and demanded nine guards. The citation cost $38,700 in fines plus overtime to scramble five more officers that afternoon.
Quick Count Formula
- Measure total slab area under roof
- Divide by 5,000 (or 2,500 if hot work)
- Round up to next whole number
- Add one guard for every 100 vertical feet of hoist or elevator shaft
- Post the count on the permit board so the marshal sees math, not magic
Hidden Savings
Batch your hot work into one zone and one shift. Torch the steel deck from 7 a.m. to 3 p.m. then switch to cold tools. You only pay the double ratio for eight hours, not the entire week.
Need help counting heads for your next pour? Call us and we will map the slab, calculate the ratio and station the exact number of certified guards before the concrete truck arrives.
