The short answer
There is no reliable one-size-fits-all ratio for construction-site security. The appropriate number of guards depends on the site’s acreage and layout, number of entrances, sight lines, public exposure, value of stored materials, hours of operation, incident history, and whether officers must remain at fixed posts. One officer may be sufficient for a compact, fenced site with a single controlled gate. A larger or divided property may require separate access-control and patrol positions.
What to know
Plan from duties, not headcount. List every required function—gate coverage, delivery verification, perimeter patrol, equipment-yard checks, and emergency communication—then determine whether one officer can perform those duties without leaving a critical post unattended. Also consider patrol travel time, break relief, shift changes, and the periods when deliveries or subcontractor traffic peak.
Portable camera towers or scheduled mobile patrols can extend visibility, but technology should not be counted as an automatic substitute for an officer who must verify people, make judgment calls, or respond under post orders. Arrow should assess the actual site before recommending staffing. The plan should be reviewed whenever the perimeter, workforce, inventory, or phase of construction changes.