What Is the Fire Watch Actually Costing You?
A fire watch feels like the cheap option because nobody sends an invoice for it on day one. Put the real numbers in and it usually overtakes the repair inside a week — and at the end of that week the system is still impaired.
At the length you have entered, you are spending more watching the building than you would spend making the watch unnecessary — and at the end of it the system is still impaired.
Overtime and shift premiums, agency margins if you hire the watch in, the manager's time supervising it, and whatever your insurer does to your premium. Every one of those pushes the real number up, never down.
How the patrol figure is worked out
A thorough patrol — looking into spaces rather than walking through them — covers roughly a thousand square feet a minute, plus a couple of minutes for each additional floor. That is an estimating figure, not a standard. A congested warehouse with racking walks far slower than an open office floor, and your AHJ sets both the interval and what counts as covered.
What the arithmetic does show reliably is when the interval is impossible. If a single lap of the building takes longer than the interval, one person cannot hold it, no matter how willing they are. That is the moment a fire watch quietly stops being a fire watch and becomes a person walking around — which is exactly the situation that gets found after an incident, not before one.
The comparison against the repair is the part worth showing to whoever controls the budget. A watch is an operating cost that nobody approves in advance and everybody pays; the repair is a capital cost somebody has to sign. That asymmetry is why buildings sit impaired for months.