Safely unloading stone slabs and other large heavy items from A-frames

This guidance explains how to control the risk of injury when unloading large heavy items from A-frames mounted on vehicles. It is for employers and employees.


Unloading large, heavy items from A-frames is dangerous

Large, heavy items like stone slabs are often transported on A-frames mounted on truck trays. Mounted A-frames are also used for window panels, concrete wall sections or other large, heavy, flat items. People have been injured while unloading items from A-frames when:

  • they were knocked off truck beds by items falling from A frames
  • slabs or items fell and crushed them when they were standing or moving on the ground near the truck
  • they became trapped between slabs or items and a side guard or wall
  • they tripped over the base or legs of the A-frame and fell from the truck bed

Hazards and risks when unloading large, heavy items

A hazard is something that can cause harm. A risk is the chance of a hazard causing harm. Harm includes injury, illness and death.

Employers must identify the hazards related to unloading large, heavy items in their workplace. Once the hazards have been identified, a risk assessment is needed to develop knowledge and understanding about the hazards and risks and how best to control them. Two of the main hazards when unloading large, heavy items are:

  • the item falling or
  • an employee falling

The load may fall

When moving large, heavy items it is easy to misjudge the speed, force and amount of movement that will happen. This can cause the load to topple. There may not be time to escape the falling load.

An employee may fall off the truck

When unloading slabs or items from an A-frame mounted on the tray of a truck, a person may fall off the truck because:

  • a slab or item has toppled away from the A frame racking and struck or crushed them. This can happen when the transport restraints are taken off the slab or item and:
    • The person is standing, working or walking through the fall shadow of the slab or item. A person may do this to attach and secure the clamp in the middle of the stone slab or item. Manual clamps increase the risk because they need the physical latch of the release trigger for the clamp to activate and grab the slab or item.
    • The truck is on uneven or sloping ground. Standing or walking on the tray can further destabilise the slabs or items.
    • Environmental conditions, like high winds, cause the slab or item to become unstable and topple.
  • they have slipped and tripped on the tray. This can happen when:
    • stepping over the base or leg of the A-frame rack while walking through or working on the tray section of the truck
    • the surface is slippery from dust or moisture
    • the truck is on uneven or sloping ground

Understanding the fall shadow

The fall shadow of a slab or other item is the area the item covers as it falls from vertical until it stops falling. It includes the item itself and all the pieces if it shatters.

The fall shadow of a slab or other item is a danger zone.

Each slab or item will have a different fall shadow. The size of the fall shadow depends on the size of the item and if there are any barriers it might hit as it falls. The fall shadow will move with the slab or item if it is moved by a crane or forklift. In some cases, extra clearance is required around the fall shadow.

The impact that a falling slab or item will have depends on its size and the speed and angle it falls. Even if the impact of the slab or item falling is low, it can still be enough to seriously injure a person.

Illustration of a stone slab and a fall shadow on each side of it.
Figure 1: Example of the fall shadow of a slab, including the additional clearance area.

Ways to control the risk when unloading large, heavy items

Risks must be eliminated, so far as is reasonably practicable. If risks cannot be eliminated, they must be reduced so far as is reasonably practicable. There are a number of ways to eliminate or reduce the risk when unloading large, heavy items.

During transport

  • When transporting very large items such as concrete wall sections, use transport A-frame racking that has support uprights. Support uprights are a physical barrier that can stop a slab or item toppling. The uprights:
    • need to be engineered to withstand the forces of a toppling item, and
    • must be left in place while unloading or while any items are on the racking
Illustration of several stone slabs stored in an A-frame rack.
Figure 2: Example of A-frame racking with support uprights
  • Use A-frame racking designed with base or legs that are angled at 90° to the A-frame arms. This helps to direct the slab or item onto the A-frame’s sloping arms.
Illustration of an A-frame storage rack showing legs at a 90 degree angle to the arms.
Figure 3: Example of A-frame racking showing legs angled at 90° to arms.

Before unloading

  • Ensure sites are prepared for delivery. There should be clear space for safe access and unloading should be done as close as possible to the installation site.
  • Install monitoring devices like a spirit level or anemometer. This can help to assess the ground or wind conditions to decide if it is safe to unload.
  • Together with the anemometer, calculate the wind load on the slab or item before unloading. Use this information to decide if it is safe to handle and unload the slabs or items.
  • Set up pedestrian exclusion zones and make sure no one is in the fall shadow before releasing transport restraints from slabs or items.
  • Use an automatic or remote start clamp. This removes the need for a person to stand in the fall shadow to release the trigger on a clamp.
  • Make sure no one enters the fall shadow at any time after the restraints are freed.
  • Ensure that any plant or lifting gear, like shackles, cables or clamps, is regularly checked by a competent person. Follow the manufacturer’s instructions on inspection procedures and frequency.

During unloading

  • Never walk in the fall shadow of a slab or item.
  • Avoid stepping over the base or leg of the A-frame racking while working on the tray section of the vehicle. Have clearly defined access and egress points to minimise the time spent on the tray and moving across the tray.
  • When unloading from an A-frame, alternate the side you are removing the slabs or items from. This avoids excess or uneven loading on one side of the A-frame.
  • Where possible, unload slabs or items using an overhead bridge crane inside the premises, protected from the elements.
  • Create a system of work that allows work to be done from the vertical edge of the slabs or items and outside of the fall shadow. For example, if using a forklift to unload, wedge apart the slabs or items from the vertical edge and then 'torpedo' unload from the truck.
Illustration showing forklift torpedo removing stone slabs from a truck.
Figure 4: Example of a forklift torpedo unloading slabs from the back of a truck.
Illustration showing forklift torpedo removing stone slabs from a truck.
Figure 5: Example of a forklift torpedo unloading slabs from the side of a truck.
  • Ensure that grippers are used according to the manufacturer's design and purpose. A gripper must not be used with more than the stated maximum number of slabs or items or weight capacity. The thickness and placement of slabs or items must not prevent the jaws from operating correctly.

Using plant and mechanical aids to unload slabs and items

The best way to unload slabs and items is by using an overhead bridge crane. If this is not possible forklifts or other mechanical aids should be used.

Using forklifts to unload slabs and items

  • The load should not be raised higher than needed to clear any obstacles. Pre-plan the travel route to avoid as many obstacles as possible.
  • Unload the truck on flat ground and plan how to avoid moving the slab up or down elevations, such as ramps.
  • Make sure the forklift has the correct load rating for all fitted attachments and is being used as intended. Using a forklift with an attachment can reduce the lifting capacity of the forklift by the weight of the attachment.
  • The forklift and pedestrian movement need to be coordinated. The pedestrian should follow the suspended slab and never be directly in the fall shadow. For example, the forklift driving in reverse so the slab is always moving away from the person.
  • The forklift driver needs to know where any person walking and steadying the slab or item is and what they are doing. The driver needs to:
    • tell the other person what they intend to do before they do it
    • monitor that person at all times, and
    • make frequent eye contact with them
  • Workers should guide slabs or items from the end furthest from the forklift. Workers should guide the slab in a way that ensures they remain outside the moving fall shadow. One way to do this is to use a boat-hook type device that can be used to both push and pull against the slab or item.
  • Ensure pedestrians, except those helping to guide movement, are not in the area that the slab or item is moving through.
  • Ensure forklifts are driven at a speed that does not pose a risk, think about:
    • the distance any pieces of the slab or item could travel if they broke off
    • how the slab or item could swing when forklift turns
    • the swept area of the slab or item and the speed of the outer edge during turning
    • using a speed limited forklift.
  • Make sure workers are given the information and training they need to use forklifts safely.

Using mechanical aids to unload slabs and items

Mechanical aids include lifting devices and trolleys. Before using a mechanical aid make sure it is fit for purpose. You should also make sure you regularly review and inspect mechanical aids to make sure they are in good working order.

Manual handling of slabs or items

If it is not possible to use a crane, forklift or mechanical aid make sure:

  • there are enough people to safely manually handle the slab or item, and
  • there is a clear plan for safely moving the slab or item, which everyone understands

Reviewing risk controls

Reviewing risk control measures will help you ensure they are working and haven't introduced new risks. Reviews will also help you identify if your controls become less effective, or if there are other controls you should introduce. Review your risk controls regularly to make sure they work as planned. Don't wait until something goes wrong.


Involving your employees in consultation on heath and safety issues can result in a safer workplace. Employers must consult with employees and contractors when:

  • identifying or assessing hazards or risks, and
  • making decisions about how to control risks which will directly affect those employees and contractors