Can I Install New Cladding Directly Over Existing Asbestos Cement Sheets?

Overclading existing asbestos cement sheets with new cladding is technically possible in some situations, but it is not a simple DIY job you can dive straight into. NZ regulations, building consent requirements, and serious health and safety obligations all come into play — and getting any of these wrong can be costly, dangerous, and potentially illegal.

What Are Asbestos Cement Sheets?

Asbestos cement (AC) sheets — often called fibrolite, Super Six, or flat asbestos sheet — were widely used on NZ homes built or renovated before the late 1980s. They contain chrysotile (white) asbestos fibres bound in cement. When undisturbed and in good condition, the risk is relatively low. However, any cutting, drilling, sanding, or breaking of these sheets releases fine asbestos fibres into the air, which are a serious health hazard linked to mesothelioma and other lung diseases.

Before you do anything, you need to confirm whether your existing cladding actually contains asbestos. If your home was built before 1990, assume it may. A licensed asbestos assessor can take samples and have them tested in a laboratory — this is the only reliable way to know for certain.

Can You Overclade Without Removing the Sheets?

In some circumstances, yes — overclading (fixing new cladding over the top of existing AC sheets) can be an acceptable approach. The key advantages are:

• The existing sheets remain encapsulated and undisturbed, reducing fibre release.
• It can be more cost-effective than full removal.
• It avoids generating asbestos waste.

However, there are important conditions and limitations:

• The existing AC sheets must be structurally sound, well-fixed, and not crumbling, cracked, or friable (easily crumbled).
• The additional cladding weight must be within the structural capacity of the framing — your engineer or builder needs to confirm this.
• The new cladding system must still comply with NZ Building Code requirements, particularly Clause E2 (External Moisture), to prevent water ingress and interstitial condensation.
• Cavity systems may be required under the new cladding depending on the product chosen — check with the cladding manufacturer.
• Future owners, tradespeople, and emergency services must be informed that asbestos is present beneath the new cladding. This is an ongoing obligation.

Building Consent — Do You Need One?

In most cases, yes, you will need a building consent to overclade your home. Recladding is generally not listed as an exempt activity under Schedule 1 of the Building Act 2004. Always check with your local council before starting work — do not assume consent is not required. You can find guidance on consent requirements at MBIE Building Performance.

Your council may also require documentation confirming the asbestos management approach as part of the consent process.

Health and Safety — The Legal Obligations

This is where things get very serious. Under the Health and Safety at Work (Asbestos) Regulations 2016, work involving asbestos is tightly controlled:

• Any disturbance of asbestos cement — including drilling fixing holes, cutting sheets, or removing damaged sections — is regulated asbestos removal work.
• Depending on the quantity and type, this work must be carried out by a licensed asbestos removalist (Class A or Class B licence, depending on the material).
• Even if you are overclading without removing the sheets, fixing through them requires drilling, which disturbs asbestos. This must be done by a licensed professional.
• Homeowners are not permitted to carry out licensed asbestos removal work on their own homes. This is a common misconception.

For full details on your obligations, refer to WorkSafe NZ, which publishes guidance on working with asbestos.

The Overclading Process — What's Typically Involved

A professional overclading job over AC sheets generally follows these steps:

1. Asbestos assessment — a licensed assessor inspects and samples the existing cladding.
2. Structural assessment — a builder or engineer checks the framing can carry the additional load.
3. Building consent application — submitted to your local council with plans and specifications.
4. Licensed work — any drilling or fixing into AC sheets is carried out by a licensed asbestos professional or under appropriate controls.
5. New cladding installation — installed by a qualified builder, following the manufacturer's specifications and NZ Building Code requirements. Products such as James Hardie fibre cement systems are commonly used and have specific installation guides.
6. Asbestos register update — the presence of asbestos beneath the new cladding must be recorded and disclosed.

Removal vs. Overclading — Which Is Better?

There is no universally right answer — it depends on the condition of the existing sheets, your budget, and your long-term plans for the property. Discuss both options with a licensed asbestos assessor and a qualified builder.

When to Call a Professional

You should engage professionals at every stage of this project. Specifically:

• A licensed asbestos assessor to identify and assess the existing material.
• A licensed asbestos removalist for any work that disturbs the sheets (drilling, cutting, or removal).
• A Licensed Building Practitioner (LBP) to carry out or supervise the new cladding installation — find one at Licensed Building Practitioners.
• Your local council to confirm consent requirements before any work begins.

You can find qualified asbestos removal specialists and licensed builders in your area on tradedirectory.co.nz.

Safety note: Never attempt to drill, cut, sand, or remove asbestos cement sheets yourself. Even brief exposure to asbestos fibres carries serious long-term health risks. Always treat suspect material as asbestos until proven otherwise.

Sources & Further Reading

• WorkSafe NZ — Asbestos guidance
• MBIE Building Performance — Building consent information
• Licensed Building Practitioners — Find an LBP
• James Hardie — NZ cladding systems
• BRANZ — Building research and technical guidance
• Standards NZ — NZ Building Standards