This guidance contains practical advice for persons conducting a business or undertaking (PCBU). It is for PCBUs such as timber manufacturers, mills or yards, and other PCBUs who stack sawn timber or board materials.
What this guide is about
Under the Health and Safety at Work Act 2015 (HSWA), you must ensure that the health and safety of workers and other people is not put at risk from your work.1
This guidance provides advice on how the health and safety risks arising from sawn timber stacks and stored board materials can be minimised through the use of:
- good site management
- safe stacking and unstacking practices, and
- safe storage options for board materials.
2.0 Managing risks
Your duties to manage work risks under HSWA
Risks to health and safety arise from people being exposed to a hazard (a source or cause of harm). A PCBU must first try to eliminate a risk if this is reasonably practicable.2 If it is not reasonably practicable to eliminate the risk, it must be minimised so far as is reasonably practicable.
Identifying, assessing and managing work risks
We recommend you follow these steps to identify, assess and manage work health and safety risks.
Step 1: Identify hazards that could give rise to work risks
With your workers, identify what could harm the health or endanger the safety of one or more workers or others (such as visitors, or bystanders).
Step 2: Assess work risks
With your workers, identify and assess the risks arising from each work hazard.
Step 3: Decide how to manage each risk
With your workers, decide how to manage work risks. Multiple control measures may be needed to deal with a given risk. Give preference to control measures that protect many workers at the same time (for example, safety barriers).
Step 4: Put control measures in place
As soon as possible after a decision is made about the control measures, a PCBU should:
- put the control measures in place
- instruct and train workers (including new workers) about the control measures, including why it is important to use them and how to apply them.
Step 5: Review and improve control measures
Control measures should remain effective, be fit-for-purpose, be suitable for the nature and duration of the work, and be carried out by workers correctly.
With your workers, regularly monitor and review control measures to confirm that the measures are effective.
See Appendix 5 for more information on managing risk.
You must involve your workers when identifying and assessing work risks and making decisions on how to eliminate or minimise work risk. For more information, see Appendix 4: Worker engagement, participation and representation.
Harm to workers and others can occur when timber stacks collapse or stored boards tip. The possible causes of these are described next.
Causes of timber stacks collapsing and stored boards tipping
Common causes of sawn timber stacks collapsing
Incidents with stacked sawn timber usually happen when timber stores collapse and heavy timber falls and crushes workers or other people. These incidents can be fatal.
Stack collapses are commonly caused by:
- Use of damaged, poor condition or insufficient bearers to support the stack.
- Poorly positioned, incorrect length or non-uniform bearers being used.
Poorly assembled, unstable stacks
- Excessive stack heights being assembled.
- Misplacement or missing fillets.
- Use of poor quality packs (for example, packs were not good quality to begin, have shifted out of shape over time, or were not strapped together appropriately).
- Incorrect strapping used to support load.
- Incorrect positioning of strapping.
Unsafe work practices or poor site design
- Vehicles knock the stack because there is not enough space to work around the stack.
- Workers climb the stack to access packs or other items stored incorrectly.
- Stacks are not monitored regularly for change and restacked if needed.
- Poor unstacking practices being used.
- Unsuitable ground conditions where stack is assembled (for example, the ground is sloped, uneven, or with poor load bearing capacity).
- Environmental factors changing the ground where the stack is assembled (for example, rain softening or washing away the ground below the stack).
- Wind moving or blowing packs off the stack.
Common causes of stored board materials tipping
Wooden sheets are often heavy and can be difficult to move. When multiple sheets are stored together, for example, leaning against a wall, the risk of several sheets tipping out of control and crushing workers or other people increases.
Incidents with board materials are commonly caused by:
Poor storage practices
For example, boards stored leaning against a wall slipping out of control and injuring workers.
Unsuitable storage systems being used
For example, systems collapsing because they were not appropriate for the load that they were supporting.
Sections 3–6 provide good practice advice on safe site management, safe stacking practices, safe unstacking practices and safe storage of board materials.
3.0 Safe site management
This section provides guidance on planning and managing your timber storage, so that risks to workers and visitors are minimised.
It describes how to have a safe site design and well located stacks, and what to check for in regular stack inspections.
It is important to think about where your timber storage area will be located, and who will be visiting or working around it.
When designing a safe work site, consider the following questions:
|How can you restrict public access?||
Where there is a risk of public access to the timber store area, consider providing appropriate fencing to keep out children and other unauthorised people.
|How can you clearly define roads and aisles, and keep pedestrians and vehicles apart?||
Roads and aisles around a site should be clearly defined and well maintained.
|Where are other workers or activities located?||
Consider where other activities are likely to be in and around the site. Where practicable, design your timber storage site so that risks to other workers or visitors are minimised.
|How can you provide clear signage?||Signs on the site directing vehicles and pedestrians should be simple, well positioned, well lit, and easy to read and understand.|
Table 1: Safe site design considerations
For more information on managing your site, see WorkSafe’s guidelines: Managing work site traffic
To minimise the risk of stack collapse, the area where a stack is located should be assessed for suitability. Consider the following:
- Ground stability
Ground below and around the stack needs to be sound and strong enough to hold the load of the stack as well as any machinery that might be used.
Ground should be flat, or if the foundation has been sloped to encourage water to drain, any slope should not exceed 2°
The site should have adequate drainage so that heavy rain will not affect the ground stability. Pooling of water can also deteriorate the bearers.
- Prevailing wind
Stacks that are outside may be affected by wind. Even relatively light wind can dislodge timber. Where possible construct them so a small cross section is facing the prevailing wind direction. If appropriate in high wind areas, upper layers of the stack can be restrained to prevent movement.
- Surface construction below stack
The surface that the stack is on should be solid and well maintained with no potholes or cracking. The foundation and soil below the stack should be fit-for-purpose for the load of the stack it will need to support.
- Access to stack
The stack needs to be accessible for whatever method will be used to assemble or unstack the stack. For example, if forklifts or side-loaders will be used on or around the stack, leave enough room around the stack to work safely.
Set stacks out so that workers can safely access and scan identification codes.
Consider what visibility pedestrians and vehicles will have once the stack has been assembled. Stack areas should have adequate lighting.
- Suitability of buildings
If buildings are to be used for timber storage, a competent person should assess their suitability. For example, the walls of storage sheds may require reinforcing.
Location of other features
- Location of power lines
Stacks should be located so that machines that work with them are further than the distances required by regulations from any live power line. For more information, see our guidance on the Electrical Codes of Practice.
- Location of underground services
Consider where underground services, manholes, fire hydrants or other site utilities are located. They may need to be accessed after the stack is built.
- Location of site boundary
When timber is stacked beside a boundary where there is public access, assemble the stack end-on and at least 1 metre from the boundary.
Training and support of workers
It is important to train workers on how to safely stack and unstack sawn timber and boards. Training should be specific to the work area and role and include:
- what the risks are
- ways for workers to report or raise issues
- refresher training and on site job observation if appropriate.
Timber storage sites and stack condition should be inspected regularly as part of general housekeeping or after an event such as an earthquake or storm.
Checks should look for change and any new or potential risks. For example, regular inspections should:
- look for change in the site surface. For example, potholes or damage from the environment or vehicles that need to be filled and repaired
- check that safe stacking practices are being used
- assess any change in stack shape or if the stack has started to lean. Restack if necessary.
- check for any pack that has begun to shift out of square. It could affect the stability of the whole stack. Assess and repack if necessary
- check bearers for damage, and replace if necessary
- assess strapping for wear and correct tensioning. Worn or loose straps should be replaced or re-tensioned to maintain the pack shape. Check that the strap being used is still suitable if the load on the stack has changed.
Stored timber boards or large flat items should be checked regularly to ensure the storage systems are not overloaded or are damaged, and that safe storage practices are being followed.
Put systems in place so that if workers see damage or instability in a timber store, it can be reported to you or a supervisor as soon as possible.
4.0 Safe stacking practices
This section describes the parts of a stack, how to safely assemble a stack, and stack height limits.
Parts of a stack
A timber stack has many parts. The following table provides a description of each part, and how to use it effectively to form a stable stack.
|Part||How to use effectively|
The foundation is the surface and layers below the stack. They help the load of the stack to be spread out to a level that the ground can support.
A solid foundation is necessary to construct a stable stack.
Concrete or asphalt foundations are preferred as they help to protect the layers of soil beneath from moisture damage.
Foundations should be fit-for-purpose and will depend on the soil type and the load that they need to support.
A competent person should assess the suitability of the foundation, and if appropriate, design what will be needed.
Bearers are large lengths of timber used to raise the lowest packs off the ground and provide space for forklifts or other plant to lift the pack. They support the weight of the stack and are an important part of keeping the stack stable.
It is important to make sure there is a stock of good quality bearers available and that damaged bearers are not being used.
Bearers/Ground Bearers should:
Do not use any bearers that protrude from the stack, or are shorter than the pack width.
Do not leave loose, unstrapped bearers on top of packs.
Packs of timber are the building blocks of the stack. The quality of the packs being used plays a large part in the overall stability of the assembled stack.
If packs must include varying lengths/widths of timber, spacers can be used to make them more uniform and more stable.
Do not leave any timber ends protruding from the pack, as this encourages people to use them to climb the stack which should be avoided.
Strapping (sometimes called banding) around the outside of a pack holds the timber lengths together firmly and helps to form a stable building block.
Binder fillets and spacers
Binder fillets are extra pieces of wood that can be used between the layers of packs to help form a tight pack.
Spacers are extra pieces of wood placed between complete packets to provide further stability and guide forklift drivers when stacking or unstacking, or when loading or unloading.
Binders and spacers use friction to help tie the packs together and can be used to even out any irregularities or unevenness such as sagging ends in the packs.
Binder fillets and spacers should:
Additional restraints can be added to a stack to help prevent the stack from moving or collapsing.
It is recommended that the
Examples of additional loads include:
Stacks that are located side-on and close to the boundary of the site should be restrained to the full height of the stack.
A competent person should:
TABLE 2: Safe stacking practices
For transporting timber on any public road, restraint methods should follow the Waka Kotahi NZ Transport Agency Truck Loading Code(external link)
Strapping and stack restraints that may be suitable for moving a stack around a site may not meet this code and should be assessed by a competent person.
Safe stack assembly
Follow these tips for safe stack assembly.
- Place smaller or lighter packs on top of larger heavier packs.
- The centre of gravity for each pack should be stacked directly above one another.
- Packs should not protrude from the stack. This encourages people to use them to climb the stack and should be avoided.
- If identification tags are required, position them so that they can be safely accessed. It is preferable to place them across the width (shortest side) of the stack, so that the risk to workers is minimised.
- Packs should not bridge across two stacks or across other packs.
- Do not place loose materials or timber on top of stacks.
- The stack should stand alone. Stacks should not lean against or be supported by each other.
- If appropriate, apply restraining devices to the height of the stack. For more information, see the section on stack restraints in Table 2: Safe stacking practices.
Limit stack height
Even when space in your site is limited, the height of stacks should be carefully considered to minimise risk to workers and other people on site.
It is important to note that the following stack height ratios are a guide.
Before assembling a stack, a risk assessment should be completed that takes into account:
- the location of the stack and the characteristics of the area
- any environmental risks
- what other activities happen in the area around the stack.
The maximum height of any stack should not be more than four times the shortest width of the pack (ratio 4:1).
Maximum stack height = ratio 4:1
For example, if the shortest pack width is 1.1 metres, then the maximum height of the stack should not exceed 4.4 metres.
If the stack is outdoors, the height should be adjusted to suit the environment and weather conditions.
Where there is a risk of vehicles knocking the stack, or if the stack may be prone to movement in an earthquake, is on a slope, or there is frequent public access, the stack height should be reduced to a maximum ratio of 2:1.
Stacks at risk = ratio 2:1
Strapping or linking packs together
You may be able to increase the stack height if you strap smaller packs together, or use bearers to link packs. Strapping or linking packs together increases the base measurement, which increases the possible stack height.
5.0 Safe unstacking practices
This section describes how to safely unstack timber including having a plan and making sure the stack remains stable during unstacking.
Inspect the stack. Have a plan on how you will unstack before you begin
- Before unstacking, inspect the stack for any signs of instability.
- Check for broken strapping, damaged bearers or fillets.
- Consider the order that packs should be removed and whether a forklift or other appropriate equipment should be used. Check whether any packs have balled, or appear to be supporting or bridging other packs.
Access the top of the stack safely
- If access to the top of the stack is required, then it should be done safely. Use appropriate equipment to access the top of the stack. For example, a mobile elevating work platform or forklift cage.
- If these are not available, and the stack has been checked for stability, a secured ladder can be used.
- For more information, see our guidance: Working at height
Maintain pack stability while unstacking
- If appropriate, take down packs layer by layer. Check for any signs of movement as you unstack.
- Do not remove individual pieces of timber from packs until they are on the ground and the working area is safe.
- Drivers should lower packets to the ground before attempting to remove any loose timber or bearers.
6.0 Safe storage of board materials
This section provides advice on how to safely store board materials, and describes two storage options:
Wooden boards and other similar flat articles can be stored horizontally on a level surface. This includes for example, doors or windows. Suitable pallets or wood/chipboard battens should be used to support them.
Pigeon hole storage
An alternative to storing boards flat is the ‘pigeon hole’ or ‘toast rack system’. In this system boards are stored in compartments to prevent sideways movement and allow individual sheets to be accessed.
It is important that these kinds of systems are:
- designed and installed by a competent person
- fixed securely to the floor
- marked with the manufacturer's maximum load information, and not loaded above this
- regularly inspected for damage.
Safe loading and unloading of board materials
Because of their size and weight, large board materials can be difficult to move and carry. They may require a wide arm span to get a good grip and can become unstable or unbalanced, particularly if it is windy.
When lying flat, they may be difficult to move because the large surface area increases friction.
To minimise the risk of injury when loading or unloading board material, appropriate handling aids (for example, panel trolleys or lifting hooks) should be used.
For more information, see our guidance: Manual handling
- For more information about HSWA and PBCU duties, see Appendix 1.
- See Appendix 2 for more information on ‘so far as is reasonably practicable’.