No — it is not safe to waterblast an asbestos cement garage wall, even at low pressure. Waterblasting disturbs the surface of asbestos-containing materials (ACM), releasing microscopic asbestos fibres into the air that can cause serious and potentially fatal lung diseases. In New Zealand, this type of work is tightly regulated under the Health and Safety at Work (Asbestos) Regulations 2016, and doing it incorrectly can put you, your family, and your neighbours at serious risk.
Why Waterblasting Asbestos Cement Is Dangerous
Asbestos cement (sometimes called fibrous cement or AC sheet) was widely used in New Zealand garages, sheds, and homes built before the mid-1980s. It contains chrysotile (white) asbestos fibres bound into a cement matrix. When the material is intact, it is considered relatively low-risk — the fibres are locked in. However, any process that abrades, cuts, drills, or pressurises the surface — including waterblasting — can break that bond and release respirable asbestos fibres into the air.
Even "low pressure" waterblasting generates enough force to erode the cement surface. Once airborne, asbestos fibres are invisible to the naked eye, can travel considerable distances on the breeze, and settle on surrounding surfaces. Inhaling them can lead to:
- Mesothelioma (an aggressive cancer of the lung lining)
- Asbestosis (scarring of lung tissue)
- Lung cancer
These diseases typically develop decades after exposure, which is why many New Zealanders are still being diagnosed today from work done in the 1970s and 80s.
What NZ Law Says
Under the Health and Safety at Work (Asbestos) Regulations 2016, asbestos removal work in New Zealand is classified as either Class A or Class B, depending on the risk level. Friable (crumbly) asbestos is Class A; non-friable asbestos cement in good condition is generally Class B — but waterblasting converts it into a high-risk activity because it actively generates airborne fibres.
Class B removalist licence holders can remove non-friable ACM, but any work that is likely to make the material friable (including high-pressure or even low-pressure water application) may require a Class A licence. WorkSafe NZ is the authority on these classifications, and you should contact them or a licensed asbestos assessor if you are unsure.
As a homeowner, you are permitted under current regulations to carry out minor asbestos work on your own home in limited circumstances (such as carefully removing a small area of undamaged AC sheet), but waterblasting is not one of those permitted activities. It is not a safe DIY task under any circumstances.
How to Identify Asbestos Cement
If your garage was built before 1990, there is a reasonable chance the wall cladding, soffit lining, or roofing contains asbestos cement. Common products included corrugated AC roofing and flat or profiled AC wall sheets. You cannot identify asbestos by sight alone — the only reliable method is laboratory testing of a sample taken by a trained professional.
Before doing any work on suspect materials, arrange an asbestos survey carried out by a licensed asbestos assessor. BRANZ has useful guidance on identifying and managing asbestos in older NZ homes.
What You Can Safely Do Instead
If your asbestos cement garage wall is dirty, mossy, or stained, here are safer alternatives:
- Leave it alone if it is in good condition — intact, painted ACM poses very low risk.
- Gentle hand-washing with a soft cloth or brush, mild detergent, and water (kept wet to suppress dust) is lower risk than waterblasting, but still requires care and appropriate PPE.
- Painting over it with a suitable encapsulating paint (check with Resene or Dulux for products suitable for ACM) can seal the surface and improve its appearance without disturbing fibres.
- Engage a licensed asbestos removalist if the material is damaged, deteriorating, or needs to be removed entirely.
PPE If You Must Handle ACM at All
If you are doing any minor, permitted work near ACM, WorkSafe NZ recommends at minimum a P2-rated respirator (not a dust mask), disposable coveralls, and gloves. Wet the surface before and during work to suppress dust. Never dry-sweep or use compressed air near asbestos materials.
Building Consent and Disposal
Removing asbestos cement cladding may or may not require a building consent depending on the scope of work and your local council's requirements. Schedule 1 of the Building Act 2004 provides some exemptions for minor work, but you should always check with your local council before proceeding. Asbestos waste must be double-bagged in heavy-duty polythene, clearly labelled, and disposed of at an approved facility — your local council or licensed removalist can advise on the nearest site.
When to Call a Professional
You should always engage a licensed asbestos removalist for:
- Any cleaning, repair, or removal of asbestos cement that involves abrasion, cutting, drilling, or water pressure
- Damaged, crumbling, or weathered ACM
- Large areas of ACM (generally more than 10 m²)
- Any situation where you are unsure of the material or the risk
A licensed asbestos assessor can survey your property, take samples for testing, and provide a management or removal plan. You can find qualified local asbestos removal specialists on tradedirectory.co.nz to get the job done safely and legally.
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