Painting a fibrous cement (FC) roof yourself is achievable for a capable DIYer — but success depends almost entirely on thorough preparation, choosing the correct paint system, and working safely at height. Skip any of these steps and you risk peeling paint, water ingress, or a trip to the emergency department.
What Is a Fibrous Cement Roof?
Fibrous cement (sometimes called fibre cement or FC) roofing is a compressed sheet or tile product made from cement, sand, and cellulose fibres. It was widely used on New Zealand homes from the mid-20th century onwards. Because it is porous and can absorb moisture, it needs a well-maintained paint coating to stay weathertight and prevent moss, lichen, and algae from taking hold in our damp NZ climate.
Important: Older fibrous cement products (generally pre-1990) may contain asbestos fibres. Before you touch, sand, or pressure-wash any old FC roof, have a sample tested by a certified asbestos assessor. If asbestos is confirmed, stop work immediately — removal and disposal is restricted work under WorkSafe NZ regulations and must be handled by a licensed asbestos removalist.
Step 1 — Safety First
Working on a roof is one of the most common causes of serious injury for DIYers in New Zealand. Before you climb up:
- Never work alone — always have someone on the ground.
- Use a properly rated safety harness and anchor system rated for roof work.
- Work on a dry, calm day — FC roofs become extremely slippery when wet.
- Use a roof ladder (one that hooks over the ridge) to spread your weight and avoid cracking tiles or sheets.
- Check WorkSafe NZ guidance on working at height before you start.
Step 2 — Check for Consent Requirements
Painting an existing roof is generally maintenance work and does not require a building consent under Schedule 1 of the Building Act. However, if you are repairing or replacing sections of roofing, different rules may apply. Always confirm with your local council if you are unsure. See MBIE Building Performance for general guidance on what work requires consent.
Step 3 — Preparation (The Most Important Step)
Poor prep is the number-one reason DIY roof paint jobs fail. Allow at least a full day for this stage.
Clean the surface
- Apply a moss and mould treatment (biocide wash) and leave it to work according to the product instructions — typically 24–48 hours.
- Pressure wash the entire roof at a low-to-medium pressure setting (high pressure can damage FC). Work from the ridge down.
- Allow the roof to dry completely — this can take several days in cooler or overcast NZ weather.
Repair damage
- Fill any cracks or holes with a suitable exterior cement filler or patching compound.
- Replace any broken tiles or sheets before painting. Painting over damaged FC will not make it weathertight.
Prime bare or porous areas
Step 4 — Choosing the Right Paint System
Not all exterior paints are suitable for FC roofs. You need a product specifically formulated for roof use — these are more flexible and durable than standard wall paints and are designed to handle UV exposure, thermal movement, and ponding water.
| Product type | Suitable for FC roofs? |
|---|---|
| Standard exterior wall paint | No — will crack and peel |
| Roof membrane / elastomeric coating | Yes — check FC compatibility |
| FC-specific roof paint | Yes — follow manufacturer's system |
| Acrylic roof paint (roof-rated) | Yes — confirm with manufacturer |
Leading NZ paint brands including Resene, Dulux, and Wattyl all offer roof paint ranges. Visit their websites or a local trade store to get the correct product data sheet and confirm the system suits your specific roof.
Always apply the number of coats specified by the manufacturer — check the product data sheet for the recommended system, as this varies by product.
Step 5 — Application
- Apply paint on a dry, overcast day if possible — direct sun can cause the paint to dry too quickly and reduce adhesion.
- Use a long-handled roller with an appropriate nap thickness for textured FC surfaces, and a brush for edges and flashings.
- Work from the ridge down, keeping a wet edge to avoid lap marks.
- Allow full drying time between coats as specified on the data sheet.
You can find rollers, brushes, safety harnesses, and roof ladders at Bunnings or Mitre 10.
When to Call a Professional
Consider hiring a qualified roof painter if:
- Your roof is steeply pitched or difficult to access safely.
- You suspect asbestos — stop work and call a licensed assessor immediately.
- The FC is extensively cracked, delaminating, or structurally compromised — a professional can assess whether painting is even appropriate or whether replacement is needed.
- You are not confident working at height — falls from roofs are frequently fatal.
- You want the job done quickly and with a workmanship guarantee.
A qualified roof painter will have the right equipment, insurance, and product knowledge to get a long-lasting result. You can find experienced local roof painters on tradedirectory.co.nz.
Master Painters NZ member
Licensed Building Practitioner (LBP)
Roofing Association of NZ (RANZ)
