Wind can kill. On construction sites, gusts can turn ordinary materials into deadly missiles, weaken structures, and make otherwise routine tasks life threatening. In the United States there is an average of about 47 wind-related deaths per year. These are not just statistics. They are coworkers, family members, and friends.
For a technical overview of wind forces, download this slide deck: Wind Forces (PPT).
True cases that teach hard lessons
- Falling cover on a tower under construction: A gust blew a cover off an enclosure. A worker up at the 400 foot level spotted it and unhooked his safety line to avoid the falling object. The cover struck him and he fell roughly 350 feet to the base.
- Demolition collapse: During demolition, two workers were cutting inside a structure when a 20+ mph north wind with 30+ mph gusts made the already weakened structure unstable. It collapsed while a worker was trying to exit.
- Aluminum concrete forms: Five aluminum forms, standing vertically and weighing about 80 pounds each, were blown over by a strong gust. A worker was knocked down and struck his head on a protruding wale bracket.
- Roof truss installation: Workers were supporting roof trusses with temporary 2 by 4 supports when an unexpected gust caused the trusses to collapse and a worker to fall to the concrete below.
Why wind matters: pressure on surfaces
Wind pressure increases with the square of wind speed. A common simple model is:
P = K V2
where P is pressure in pounds per square foot (psf), K is a constant (about 0.0033) and V is wind speed in miles per hour. Because of the square relationship, doubling wind speed quadruples the pressure on a surface.
| Wind speed (mph) | Pressure (psf) approx. |
|---|---|
| 20 | 1.3 psf |
| 75 | 18.5 psf |
| 150 | 74 psf |
| 155 | 79 psf |
These pressures act over the entire face of an object. A large vertical form, a roof panel, or a stack of trusses can experience huge net forces even at moderate wind speeds.
Practical steps to reduce wind risk
Wind safety is a mix of planning, controls, and the right culture. Use these practical steps on every project:
- Plan for wind. Check forecasts and local conditions before starting high risk work. Have contingency plans for increasing wind speeds.
- Secure materials and equipment. Lay panels flat, lock down forms, tie down loose materials and secure covers. Store lightweight items in windproof areas.
- Anchor temporary elements. Use adequate bracing and anchorage for forms, scaffolds, and trusses. Never rely on a single weak connection.
- Control work when gusts are present. Consider suspending roof or truss work when gusts exceed safe thresholds. Consult equipment and manufacturer guidance for lift limits.
- Use taglines and spotters. On lifts and hoists, use taglines to control suspended loads and assign trained spotters to watch for gusts.
- Keep people clear of fall paths. Assume that anything aloft could fall. Establish exclusion zones beneath work at heights.
- Never unhook to avoid falling objects. If an object is falling, do not remove your fall protection to dodge it. Training and emergency procedures should emphasize staying connected.
- Inspect structures after wind events. Even moderate winds can weaken partially demolished or partially completed structures. Inspect before reentry.
- Give stop work authority. Empower any worker to halt work when wind creates an unsafe situation.
Toolbox talk checklist for wind
- Review forecast and current wind speed before starting.
- Confirm anchorage and tie-downs are in place.
- Identify exclusion zones below suspended work and remove nonessential personnel.
- Agree on hand signals and communications for gusty conditions.
- Decide in advance when to stop roof or exterior work.
Simple rules of thumb
- Expect pressure to rise fast as wind speeds increase. Small increases in speed can cause big increases in force.
- Lightweight, tall, or broad-face items are the biggest airborne hazards.
- When in doubt, secure and pause. It is far safer to delay a lift or truss set than to respond to an emergency.
Wind is an invisible hazard until it is not. By understanding how pressure grows with speed, learning from real incidents, and using practical controls, we can keep crews safer and prevent tragedies.
Want a deeper dive? Download the Wind Forces slide deck for diagrams and calculation details you can use in toolbox talks and safety plans.
Work safely. Look up. Keep each other safe.