No Australian law names a height at which safety mesh becomes compulsory. The duty is to control the risk of a fall, and the model Code of Practice states that control measures are needed wherever there is a risk of injury, irrespective of fall height. Where the hazard is falling through the roof, mesh is the recognised control. It must comply with AS/NZS 4389 and be used with edge protection or fall arrest.
In short
- Mesh controls falling through the roof. It does nothing about falling off the edge.
- It must comply with AS/NZS 4389, which sets the wire, the spacings and the lap rules.
- The crew fixing the mesh need their own fall protection before any mesh exists.
- Cover it with cladding as soon as reasonably practicable.
- On a commercial roof it also carries the insulation blanket.
That opening is the honest answer, and it is more useful than a number. The question builders actually need answered is when mesh is the right control and what makes it compliant. This covers both.
Where the duty comes from
Work health and safety law places a duty on the person conducting the business or undertaking to eliminate the risk of a fall, or to minimise it so far as is reasonably practicable. The model Code of Practice for managing the risk of falls at workplaces sets out the order to work through:
- Can the work be done on the ground instead?
- Can the fall be prevented by working on solid construction with safe access?
- If not, provide a fall prevention device such as guard rails.
- If that is not reasonably practicable, provide a work positioning system.
- If neither is reasonably practicable, provide a fall-arrest system.
Safety mesh sits in that structure as a fall protection measure for the specific hazard of falling through a roof, and the code lists permanent safety mesh as a design measure that reduces risk for the life of the building, not just during construction.
Note that construction work involving a risk of falling more than a set height is classed as high risk construction work and needs a safe work method statement before it starts. The trigger height and the regulations differ between states and territories, and Victoria runs its own OHS Regulations rather than the model WHS Regulations, so confirm the current figure with your regulator rather than a rule of thumb from another state.
Who carries the responsibility
More than one party usually has a duty at the same time, and duties are not transferable by contract.
| Party | What they are usually responsible for |
|---|---|
| Principal contractor or builder | The site as a whole, coordinating controls between trades, and the safe work method statement for high risk construction work |
| Roofing contractor | The system of work on the roof, the controls their own crew relies on, and installing mesh to the manufacturer's instructions |
| Designer | Designing out the risk where practicable, including specifying permanent mesh for future maintenance access |
| Supplier | Supplying mesh that meets AS/NZS 4389 and providing the product information to prove it |
| Building owner | Ongoing safe access for maintenance once the building is in use |
When safety mesh is the right control
Mesh earns its place where the exposure is falling through the roof plane rather than off the edge of it:
- Laying sheets on purlins. Until the cladding is fixed, the roof is a grid of open bays. Mesh turns that into a surface that will catch a person.
- Roofs that will need maintenance. The code notes that securely fixed mesh gives long term protection for maintenance and repair workers, years after the builder has left.
- Commercial and industrial roofs. Factories, warehouses, schools, office blocks and shopping centres are the typical applications, where purlin spacing is wide and the fall is a long one.
- Roofs carrying insulation. Mesh also supports the roofing blanket, which is why it appears in the same order of works as the blanket and spacers.
What safety mesh does not do
This is the part that gets people in trouble. The model Code of Practice is blunt: safety mesh does not prevent falls from the edge of a roof or through holes in a roof, so it should always be used together with appropriate edge protection, guard rails or fall-arrest systems.
Two more limits worth writing into your safe work method statement. The crew installing the mesh are themselves working at height before any mesh exists, so they must be protected by scaffolding, an elevating work platform or fall arrest while they fix it. And the mesh should be covered by the roof cladding as soon as reasonably practicable after installation, because exposed mesh invites people to treat it as a walking surface.
It is also not a working platform. Mesh is designed to arrest a fall once. Using it as somewhere to stand while working is not what it is tested for.
What compliant mesh looks like
AS/NZS 4389:2015 Roof safety mesh sets the manufacturing and installation requirements. The key numbers from the standard:
| Property | Requirement |
|---|---|
| Nominal wire diameter | 2.00 mm |
| Longitudinal wire spacing | 150 mm, tolerance ±5 mm |
| Transverse wire spacing | 300 mm, tolerance ±5 mm |
| Minimum tensile strength | 450 MPa transverse, 500 MPa longitudinal |
| Galvanising | To AS/NZS 4534, Class W02, minimum zinc coating 35 g/m² |
| Construction | Electric resistance welded under pressure, free from sharp edges and burrs |
You will see the tensile figure quoted as a flat 450 MPa in a lot of guidance, including the model code. The standard itself splits it, with the higher 500 MPa applying to the longitudinal wires that carry the load in a fall. Worth knowing when you are comparing a cheap import against a mesh that states compliance.
Roof Bloc 300 Roof Safety Mesh is 100% Australian manufactured from 2.0 mm high tensile galvanised wire rated over 500 MPa, complies with AS/NZS 4389:2015 and is designed for installation as a permanent fixture. It is supplied in 1800 mm, 2250 mm and 2400 mm wide rolls covering 90 m², 112.5 m² and 120 m².
Installation: the lap rules
Most of the strength of an installed mesh system is in the joins. AS/NZS 4389:2015 ties the side lap to the purlin spacing, because the wider the span, the more work the lap has to do:
| Purlin spacing | Minimum side lap | Fastening of the lap |
|---|---|---|
| Less than 1200 mm | One mesh spacing | As specified in the standard |
| 1200 mm to 2200 mm | One mesh spacing (150 mm) | Ring fasteners of at least 1.90 mm wire at maximum 900 mm centres between each purlin, on one side of the lap |
| Greater than 2200 mm | Two mesh spacings (300 mm) | Ring fasteners of at least 1.90 mm wire at maximum 600 mm centres between each purlin, on both sides of the lap |
The standard also notes that fastening of the laps should be carried out from underneath.
Fixing to steel and to timber
The standard sets out how the longitudinal wires are secured to the roof members. On timber, it specifies galvanised staples of at least 3.15 mm wire, driven at least 30 mm into the side of the rafter or 40 mm where they are stapled on top, at a maximum spacing of 155 mm. Where neither the primary nor the secondary fixing method can be used, longitudinal wires may be secured with galvanised steel tying wire of at least 3.15 mm diameter, wrapped and twisted with at least three complete turns.
None of this replaces the manufacturer's instructions or the standard itself. If your project relies on the detail, buy the standard and follow it, because the fixing is what turns a roll of wire into a fall control.
Mesh and insulation together
On a commercial roof the mesh is not only a safety item. The insulation blanket is laid over it, which means the mesh is also part of the thermal build up. If the sheeting then presses the blanket down onto the mesh, the blanket loses its thickness and most of its R-value at every purlin line.
That is why an insulation spacer such as the Roof Razor Insulation Spacer is used to hold the blanket at full recovery between the mesh and the metal deck. Order the mesh, the blanket and the spacers together, in matching depths. The full sequence is in our guide to metal roof insulation in Australia.
Inspection, damage and reuse
Mesh is a control that stays in the building for decades, so it is worth treating as an asset rather than a consumable.
- Check the mesh is continuous over the area to be roofed before any sheeting goes on, with no unlapped runs and no missed fixings.
- Do not use mesh with broken welds, cut wires, heavy corrosion or previous fall damage. Once it has arrested a fall it has done its job.
- Cut openings for penetrations after the mesh is fixed, not before, and reinstate the edges around the opening.
- Where a roof is being re-sheeted, treat the existing mesh as unknown until inspected. Old mesh may predate the current standard.
How much mesh to order
Work out the roof area, then add for laps. A 1800 mm wide roll with a 150 mm side lap gives about 1650 mm of effective cover per run, so a 90 m² roll covers roughly 82 m² once lapped. On wide purlin spacings needing a 300 mm lap, allow closer to 1500 mm effective width. Add end laps and offcuts around penetrations on top of that.
Worked example. A 1,200 m² warehouse roof, purlins at 1,800 mm centres, so a 150 mm side lap applies. Using 1800 mm x 50 m rolls: effective cover per roll is about 82 m², so 1,200 divided by 82 is 14.6 rolls. Add for penetrations and offcuts and order 16. Ordering the exact roof area and nothing more is the classic way to end up one roll short on the last day.
Pricing a full commercial roof package? Mesh, blanket and spacers usually go on the one order, and they need to arrive in the right sequence.
Browse roofing and safety mesh and roofing blankets, or send us the roof area and purlin spacing and we will work out quantities.
Frequently asked questions
When is roof safety mesh required in Australia?
Whenever the risk of a person falling through a roof has to be controlled and mesh is the reasonably practicable control. Australian WHS law sets a duty to manage fall risk rather than naming a height for mesh specifically, and the model Code of Practice states that control measures are needed wherever there is a risk of injury, irrespective of fall height.
Is safety mesh enough on its own?
No. It does not stop a fall from the edge of the roof or through an existing hole. It has to be used with edge protection, guard rails or a fall-arrest system.
What standard does roof safety mesh have to meet?
AS/NZS 4389 Roof safety mesh, which covers design, construction, testing and installation for domestic, commercial and industrial buildings.
What size is roof safety mesh?
Commonly 1800 mm, 2250 mm or 2400 mm wide in 50 m rolls, covering 90 m², 112.5 m² and 120 m², with 150 mm longitudinal and 300 mm transverse wire spacing.
Can safety mesh be walked on?
It is designed to arrest a fall, not to be used as a working platform. Installers must be protected by other means while fixing it, and the cladding should cover it as soon as reasonably practicable.
Does safety mesh support the insulation?
Yes, on a commercial roof the blanket is laid over the mesh. An insulation spacer is then used so the sheeting does not compress the blanket and destroy its R-value.
How much do the side laps overlap?
It depends on the purlin spacing. Under 1200 mm, one mesh spacing. Between 1200 mm and 2200 mm, one mesh spacing of 150 mm. Over 2200 mm, two mesh spacings of 300 mm, with ring fasteners on both sides of the lap.
Can safety mesh be reused after a fall?
No. Mesh that has arrested a fall, or that has broken welds, cut wires or heavy corrosion, should be replaced rather than reinstalled.
Sources
- AS/NZS 4389:2015, Roof safety mesh (Standards Australia and Standards New Zealand)
- Safe Work Australia model Code of Practice, Managing the risk of falls at workplaces, section 4.3 Safety mesh
- Model WHS Regulations, high risk construction work and safe work method statements. Check your state or territory regulator for the version that applies to you.
- Product data from the manufacturers of the products listed above
This is general information, not safety advice for a specific site. Roof work is high risk and the requirements vary between states and territories. Confirm your obligations with your regulator and your own safe work method statement.