Roof Safety Mesh: What It Is, When It Is Needed, and What Happens on a Re-Roof

How safety mesh works

The mesh is rolled out across the purlins in runs, joined along its edges, and fixed and tensioned at the ends of each run so it acts as a net rather than a loose sheet of wire. The insulation blanket is laid on top of the mesh, and the roof sheeting goes on top of the blanket.

The Australian and New Zealand Standard for roof safety mesh is AS/NZS 4389:2015, which is still the current edition (Standards Australia lists it as pending revision). It covers the mesh itself and how it is installed, including how runs are joined and fixed. The detail on site comes from the manufacturer’s installation guide. InfraBuild’s Roofsafe installation flyer, for example, sets the side lap by purlin spacing: 150mm with no fasteners below 1200mm, 150mm fastened at no more than 900mm centres from 1200 to 2200mm, and 300mm fastened at 600mm centres above 2200mm. End joins run the full width with 300mm tails, the wires joined and twisted together.

Where safety mesh is used

Falling through a roof is one of the recognised fall risks in NSW work health and safety law, alongside falling from an edge. SafeWork NSW’s code of practice Work on roofs: commercial and industrial buildings, which commenced on 22 May 2026 and replaces the 2009 Safe Work on Roofs Part 1 code, covers fragile roofs, and where mesh is used it prefers full-length runs from gutter to gutter. The general Code of Practice: Managing the risk of falls at workplaces (August 2019) still applies alongside it.

In practice, mesh turns up in three situations:

• New metal roofs on commercial and industrial buildings. Mesh goes down ahead of the sheeting, so the people laying sheets are protected against falling between purlins while the roof is still open.
• Under translucent sheeting and skylights. These are fragile. On an older roof, the mesh under a brittle skylight sheet may be the only thing between a maintenance worker’s foot and the floor.
• Re-roofs. Old mesh is either kept, if it is in sound condition, or replaced as part of the new roof.

Whether a particular project needs mesh is decided by whoever controls the work, through the falls risk assessment and the project specification. If a specification you are pricing calls it up, it is in scope.

What safety mesh does not do

Mesh controls falls through the roof. It does nothing about falls off the edge, or from plant platforms, or at a parapet. People working on top of the roof still need edge protection, guardrails, walkways or anchors, which are covered under roof height safety systems.

Nor is mesh a reason to walk anywhere on a roof. It is the last line of protection, not a walking surface.

Safety mesh and the insulation blanket

Because the blanket sits directly on the mesh, the two are linked in three ways that matter on a commercial roof.

Support. The mesh holds the blanket up between purlins. Where mesh has sagged or broken, the blanket sags with it and stops performing as designed.

Thickness. If the roof sheet is fixed straight onto the purlins, the blanket is squashed at every purlin line. Roof spacer systems raise the sheet above the purlin to leave room for the blanket between mesh and sheet. That decision is made at the same time as the mesh decision on a re-roof.

Moisture. Condensation forms on the cold underside of roof sheeting. A wet blanket lying on steel wire keeps that wire wet, which is how mesh corrodes on roofs that otherwise look sound from above.

Re-roofing over existing mesh

This is where safety mesh stops being a product question and becomes a scope and price question.

The mesh is your protection during the strip. When the old sheets come off a large industrial roof, the people removing them are standing on a roof that is progressively being opened up. The mesh underneath is what stands between them and the floor if they step or fall between purlins. If that mesh is corroded through, the protection is not there at exactly the moment it is needed.

So the mesh has to be assessed before the strip is planned, not discovered during it.

Replacing mesh means replacing the blanket. The blanket sits on the mesh, so new mesh means the old blanket comes out. On an older industrial building that blanket is often damp, compressed or degraded anyway. Budget for both together.

The sequence changes. On an operating site the roof is replaced bay by bay. Where mesh is being replaced, each bay goes old sheet off, old blanket and mesh out, new mesh in, new blanket, new sheet, with the bay protected before the crew moves on. That takes longer per bay than a straight re-sheet, and the programme has to allow for it.

Corrosive buildings wear mesh faster. Processing plants, wash bays, pool halls and any building with heat, humidity or chemical fumes inside put the mesh in a harsher environment than a dry storage warehouse. Expect to find more corrosion on those roofs.

For how a staged industrial re-roof runs on a working site, see industrial roof replacement.

How to check existing mesh

You can do a first check yourself, from the floor or a platform inside the building:

• Rust staining on the mesh, particularly where it touches the blanket or the purlins
• Broken or missing wires, or runs that have pulled away from their end fixings
• Sagging between purlins, often with the blanket sagging too
• Gaps where mesh was cut for penetrations, skylights or plant and never made good
• Daylight or water staining at the same locations

If you see any of these, have it assessed properly before the roof is priced. Mesh condition belongs in a commercial roof inspection, looked at from underneath, not only from on top.

Frequently asked questions

What is roof safety mesh made of?

Galvanised steel wire, supplied in rolls and installed across the purlins under the roof sheeting. AS/NZS 4389:2015 sets the requirements.

Is roof safety mesh compulsory?

Falls through a roof are a risk that has to be controlled under NSW work health and safety law. Mesh is a common way of controlling it on commercial and industrial metal roofs. Whether it is required on a given project is set by the risk assessment and the specification.

Does the insulation go above or below the mesh?

Above. The blanket is laid on the mesh, and the roof sheeting goes on top of the blanket.

Can old safety mesh be left in place during a re-roof?

Only if it is in sound condition. Corroded, broken or loose mesh cannot be relied on, and it is relied on most during the strip.

Does safety mesh replace guardrails or anchor points?

No. Mesh controls falls through the roof. Falls from edges are controlled with guardrails, walkways or anchor systems.

Get the mesh checked before the re-roof is priced

A re-roof quote that has not looked at the mesh is a quote that can change once the first sheets come off. Austek replaces industrial and commercial roofs across Sydney and NSW, and has done since 2010. Send us the site address and a photo of the underside of the roof, and we will factor the mesh into the re-roof scope.

Ask us to check the mesh before your re-roof is priced, or call 0411 922 441.