Why You Should Never Walk on a Corrugated Fibre-Cement Roof
Corrugated fibre-cement roofing is common on older homes, sheds, workshops and commercial buildings throughout New Zealand. Many of these roofs contain asbestos, but even when their asbestos content has not been confirmed, they must still be treated as potentially brittle.
The critical safety message is simple: never walk directly on a corrugated fibre-cement roof.
A sheet may look solid from above. It may be painted, appear undamaged and have supported someone previously. None of that proves it can safely support a person today. Age, weathering, moisture, corrosion around fixings and unseen damage can weaken the sheets. Failure can be sudden and without warning.
“Just walk along the nail lines” is not a safe method
During a recent asbestos survey of a large commercial property in Gisborne, I was shown the proposed roof access and told I could walk along the fixing lines. The site contained several warehouses with approximately 15,000 m² of corrugated fibre-cement roofing.
I refused to walk on it.
The roofing was old, extensively weathered and painted white. From some viewing positions, it was difficult to determine whether it was original fibre cement or a later replacement product. A representative later disclosed that they had previously fallen through part of the roof—demonstrating exactly why appearance and familiarity cannot be relied upon.
Walking over the fixings, nail lines or presumed purlin positions does not turn brittle sheets into a safe working platform. You may not know the precise location or condition of the supporting structure, and the sheet can still fracture beneath or beside your foot.
Why corrugated fibre cement becomes dangerous
Fibre-cement sheets are relatively thin and are supported at intervals by the structure beneath them. Over decades, their ability to support weight can be affected by weathering, moisture, biological growth, corrosion around fixings, previous foot traffic, impact damage, hidden cracking, alterations and deterioration of the supporting structure.
Painted coatings can also conceal the material’s age and condition. A roof that looks tidy from the ground may be severely weathered or damaged underneath the coating.
WorkSafe New Zealand identifies corrugated asbestos cement as brittle roofing. Its roof-safety guidance warns that asbestos-cement sheeting can shatter without warning under a person’s weight and that access should not occur until suitable hazard controls have been implemented.
The danger is therefore not limited to asbestos exposure. The immediate and potentially fatal risk is falling through the roof.
A harness alone does not make the roof safe
A common misconception is that wearing a harness makes it acceptable to walk over brittle roofing. A harness is only one possible component of a properly designed height-safety system. It does not strengthen the roof or prevent a sheet from breaking beneath you.
Any necessary access must be planned by competent people using controls appropriate to the building and the work. Depending on the circumstances, this may involve scaffolding, a mobile elevating work platform, temporary work platforms, roof ladders or crawling boards, edge protection, safety nets, restraint systems or other engineered controls.
This is specialist work. It should never be improvised by a homeowner, contractor, property manager or surveyor simply because the task will “only take a minute.”
Paint does not prove that a roof has been replaced
Paint can make an old fibre-cement roof look much newer than it is. From a distance, a coated roof may even be mistaken for metal roofing.
At the Gisborne site, the roofing had reportedly been replaced. Closer inspection indicated that substantial areas were still the original corrugated fibre-cement roofing. This is why verbal assurances, appearance and assumptions about previous building work are not enough.
Not every fibre-cement product contains asbestos, but many older corrugated fibre-cement roofs do. It is not normally possible to confirm whether a material contains asbestos by sight alone. Where the material is uncertain, it should be assessed properly and, where appropriate, sampled under controlled conditions by a competent asbestos surveyor.
When asbestos-cement roofing is broken, drilled, cut, crushed or pressure washed, asbestos fibres may be released. Damaging the roofing while attempting to inspect it can therefore create both a fall hazard and an asbestos-exposure hazard.of
An asbestos survey still needs to gather sufficient information about the roof, but that does not automatically require walking across it. Safer options may include inspection from ground level, viewing the roof from an adjacent safe location, inspecting its underside from inside the building, using suitable internal or external platforms, accessing it from a mobile elevating work platform, or using drone photography.
On the commercial site described above, I inspected the roofing using a drone and several safe internal access points. Representative samples could be collected without walking across the sheets.
A drone cannot confirm whether a material contains asbestos—laboratory analysis is required for that. However, aerial imagery is extremely useful for understanding the roof layout, locating different sheet types, identifying repairs and penetrations, recording visible damage and deciding where closer inspection or sampling may be required.
Where part of a roof cannot be safely accessed, that limitation should be recorded. Further investigation can then be recommended when appropriate access arrangements have been established.
What building owners and property managers should do
If your building has a corrugated fibre-cement roof, treat it as brittle and prevent uncontrolled access. Never instruct workers to walk along the fixings, nail lines or presumed purlins.
Clear warning signage should be displayed, and the hazard should be communicated to anyone who may need to access the roof. The roofing should also be included in the building’s asbestos information and management arrangements where applicable.
Before maintenance, refurbishment or demolition begins, arrange a professional assessment and use remote inspection or safer-access methods wherever reasonably practicable.
Refusing unsafe access is not being difficult or overly cautious. No inspection, sample or photograph is worth somebody falling through a roof.
Do you need a corrugated roof assessed?
Asbestos Safe Consultancy provides independent asbestos surveys and sampling across Hawke’s Bay, Gisborne, Taupō and the Manawatū. We do not undertake asbestos removal, so our advice remains independent and focused on identifying the material, assessing the situation and helping you understand the next steps.
If you have an older corrugated fibre-cement roof that needs to be assessed before maintenance, refurbishment, demolition or purchase, contact Asbestos Safe Consultancy to discuss a safe and appropriate approach.