Tower cranes and strong wind: what to do before and after a storm

In brief

• Strong wind puts forces on the jib, the mast and the load, and can endanger the stability of the crane and the people working near it.
• The wind limits for working are set in the manufacturer’s data sheet, in the regulations and in the instructions of those responsible on site.
• Before a storm, leave the crane in free slewing (weathervaning) mode, with no load on the hook and no loose objects on site.
• After a storm, inspect the crane before returning to work, and call for a professional inspection if in any doubt.

Winter in Israel brings days of strong wind and storms, and a tower crane is one of the structures most exposed to wind on a building site. Preparing properly before the storm and inspecting methodically afterwards are a basic part of managing site safety. In this article we explain how wind affects a tower crane, who decides when to stop work, and what to do before and after a storm.

How wind affects a tower crane

A tower crane is built to withstand wind loads, but only within the conditions the manufacturer has defined. Wind acts on the crane in several ways:

• On the structure: wind pushes on the jib, the counter-jib and the mast, adding load to the base and to the ties to the building.
• On the load: a load with a large surface area, such as formwork panels or pallets, can swing and spin in the wind, making precise control harder.
• On slewing: a crosswind makes it harder to slew the jib and to stop it in the right place.

It is important to remember that wind at jib height is usually stronger than wind at ground level. What feels like a light breeze next to the site manager’s cabin can be a much stronger wind at the top of the crane.

Who decides when to stop

The decision to stop work in wind is not a matter of feel. It rests on three sources:

1. The manufacturer’s data sheet and instructions: for each model, the manufacturer sets the wind limits for working, for erection and for the out-of-service condition. These are the binding figures for the specific model.
2. The regulations: the Safety at Work (Tower Cranes) Regulations, 1966, generally prohibit operating a tower crane, or erecting, raising or dismantling it, in wind that may endanger its stability or the workers. See also the guidelines and publications of the Occupational Safety and Health Administration on the Ministry of Labor website.
3. Those responsible on site: the site manager and the crane operator decide in practice when to stop work, according to the measurement, the manufacturer’s instructions and conditions on the ground. Even when the reading is below the limit, an operator who cannot control the load safely must stop.

We do not publish general wind-speed figures here, because they differ from model to model. The binding values must be taken from the data sheet and the manufacturer’s instructions for the specific model. The regulations prohibit working in dangerous wind but do not state a number.

Measuring at working height, and a smart wind vane

Because wind changes with height, the relevant measurement is at jib height, not on the ground. For this, an anemometer is fitted at the top of the crane, showing the operator the wind speed and warning when it approaches the limit. A smart wind vane adds the wind direction to the measurement and can keep a history of readings. Advanced systems can combine the wind data with the crane’s safety systems, so that the site manager also receives an alert. Details of the safety systems RMA integrates are on the anti-collision systems page.

Preparing for a storm

Free slewing (weathervaning)

When the crane is not working, the jib should be free to turn with the wind, like a weathervane. In this state the jib lines up with the wind direction and the load on the structure is smaller. So at the end of the working day, and certainly before a storm, the slewing mechanism must be set to free mode according to the manufacturer’s instructions.

• Never tie the jib to the building or block slewing in any other way.
• Make sure there are no obstacles in the full slewing circle of the jib and counter-jib: buildings, neighbouring cranes or power lines.
• On sites with overlapping cranes, the height differences between them must allow each crane to slew freely without touching the other, including the hoist rope and hook of the higher crane. So raise the hook and position the trolley according to the manufacturer’s instructions. The anti-collision system does not work when the crane is disconnected from power and slewing freely.

Securing loads and the hook

• Never leave a load hanging on the hook. The regulations prohibit the operator from leaving the operating station while a load is suspended.
• Raise the hook and position the trolley according to the manufacturer’s instructions.
• Return the control levers to zero and disconnect the power supply at the crane’s main switch, as the regulations require. Aircraft warning lights, if fitted, should stay powered from a separate circuit and not switch off with the main switch.
• Secure loose materials, boards, sheeting and signs on site that could fly off and hit the crane or people.
• Signs and sheeting on the crane itself increase the surface area exposed to wind, and should be fitted only with approval and according to the manufacturer’s instructions.

Getting ready before winter starts

It is best not to wait for the first forecast. Before the season, it is recommended to check that the anemometer is working and calibrated, that the free-slewing mechanism works properly, that drainage around the base prevents water from collecting, and that everyone on the team is clear on who decides to stop work and how the crane is put into its out-of-service condition.

Inspection after a storm

Before returning to work, the crane operator carries out the daily inspection as usual, and after a storm special attention should be paid to the following points:

• The base: settlement, standing water or erosion around the chassis or the foundation.
• The ties to the building: bolts, pins and anchor points.
• The counterweights: that they are in place and secured.
• The jib and mast structure: deformation, impact damage or loose parts.
• Electrical and safety systems: limit switches, the anemometer and the anti-collision system.
• A trial run without a load, checking that the brakes work properly.

If there is any unusual finding or doubt, do not operate the crane until it has been checked by a professional service team and, where necessary, by a certified inspector. As of 2026, RMA provides ongoing service to about 500 cranes across the country, with a team of 60 staff, technicians and engineers. Details are on the technical service for cranes page, and more information is in the article How to maintain a tower crane: a guide for contractors. To request a service call, phone 08-9202882 or send a WhatsApp message.

Frequently asked questions

At what wind speed do you stop working with a tower crane?

There is no single figure for all cranes. The wind limits are set for each model in the manufacturer’s data sheet, and the regulations and the instructions of those responsible on site also apply. Follow the values for the specific model.

What is weathervaning on a tower crane?

It is a free-slewing mode in which the jib can turn with the wind like a weathervane. The jib then lines up with the wind direction and the load on the structure is smaller. The crane is set to this mode at the end of work and before a storm.

Is it permitted to tie the crane jib to the building before a storm?

No. Tying the jib prevents it from turning with the wind and can greatly increase the load on the crane. Leave the slewing mechanism in free mode according to the manufacturer’s instructions.

Why measure wind at jib height?

Because wind at height is usually stronger than at ground level. An anemometer at the top of the crane shows the operator the conditions at the actual working height.

What do you inspect on a crane after a storm?

The base, the ties to the building, the counterweights, the jib and mast structure, and the electrical and safety systems, followed by a trial run without a load. If in any doubt, call for a professional inspection.

Who decides to stop work in wind?

The site manager and the crane operator, based on the wind measurement, the manufacturer’s data sheet and the regulations. An operator who cannot control the load safely must stop even if the reading is below the limit.

The information in this article is general only and is not engineering, safety or legal advice. Before any decision, follow the manufacturer’s instructions and the applicable law, and consult certified professionals.