How to Paint a Fibrous Cement Soffit That Is Chalking Badly

Badly chalking fibrous cement soffits are a common headache on older New Zealand homes, but the good news is that with the right preparation and products, you can get a durable, good-looking result yourself. The key is that preparation does at least 80% of the work — skip it and your new paint will fail just as quickly as the old coat.

What Is Chalking and Why Does It Happen?

Chalking is the powdery, white residue that forms on the surface of old paint as UV light and weathering break down the paint binder over time. On fibrous cement (sometimes called FC or fibre cement) soffits, it's especially common because soffits are often painted with cheaper or incorrect coatings, or the original paint has simply reached the end of its life. Running your hand across the surface and seeing white powder transfer is the classic test.

Left untreated, chalking prevents new paint from bonding properly, leading to peeling and flaking within months.

Safety First

Before you start, check whether your home was built before the mid-1980s. Older fibrous cement products — particularly those made before around 1984 — may contain asbestos fibres. If you're unsure of the age or origin of the material, do not sand or dry-scrub it. Have a sample tested by a licensed asbestos assessor before proceeding. WorkSafe NZ has clear guidance on working safely around asbestos-containing materials.

Also, working overhead on a ladder carries real fall risk. Use a stable, correctly rated ladder or scaffold, and never overreach.

Tools and Materials You'll Need

• Stiff-bristle brush or broom
• Garden hose or pressure washer (low setting)
• Sugar soap or a dedicated surface cleaner
• Clean rags or sponges
• Alkali-resistant or FC-specific primer
• Quality exterior topcoat (low-sheen or flat recommended for soffits)
• Roller (short-nap, 10–12 mm) and/or quality synthetic brush
• Drop sheets and masking tape
• Safety glasses, gloves, and a P2 dust mask

Step 1 — Remove the Chalk Thoroughly

This is the most critical step. Loose chalk must be completely removed or your new paint simply won't stick.

1. Dry brush the entire soffit with a stiff bristle brush to knock off loose material.
2. Wash down with a hose or low-pressure washer. A pressure washer on a gentle setting works well, but keep the nozzle moving and don't hold it too close — fibrous cement can be damaged by high-pressure water at close range.
3. Mix sugar soap with warm water and scrub the surface with a brush or sponge to cut through any grease, dirt, and remaining chalk residue.
4. Rinse thoroughly with clean water and allow the surface to dry completely — typically 24–48 hours depending on conditions. Painting onto damp fibrous cement is a common cause of paint failure.

Step 2 — Inspect and Repair

Once clean and dry, look for:

• Cracks or chips — fill with a flexible exterior filler suitable for fibre cement, following the manufacturer's instructions.
• Bare or raw edges — these are highly porous and must be sealed.
• Any signs of moisture damage or delamination — if the board is soft, swollen or crumbling, it may need replacing. Check with a qualified painter or builder.

James Hardie publish technical data sheets for their fibre cement products that include guidance on repair and repainting — worth checking if you know the brand of your soffit.

Step 3 — Apply a Quality Primer

Primer is non-negotiable on a chalking surface. Choose a primer specifically suited to fibre cement or masonry:

• Alkali-resistant primer is important because fibrous cement is alkaline, and the wrong primer can cause adhesion failure or discolouration.
• Resene and Dulux both offer primers designed for fibre cement and masonry substrates — ask in-store for their current recommendation for your specific situation.
• Wattyl also has exterior primer systems suitable for this substrate.

Apply primer generously, working it into the surface. Pay extra attention to any repaired areas and raw edges. Allow to dry fully per the manufacturer's stated recoat time.

Step 4 — Apply the Topcoat

For soffits, a low-sheen or flat exterior acrylic is generally recommended — high-gloss finishes tend to highlight surface imperfections and are harder to touch up. Apply two full coats, allowing proper drying time between coats.

Use a short-nap roller for flat sections and a brush to cut in around edges and joins. Work methodically across the soffit to maintain a wet edge and avoid lap marks.

Step 5 — Clean Up and Inspect

Once the final coat is dry, inspect for any missed spots, thin areas, or runs. Touch up as needed. Clean brushes and rollers with water (for water-based paints) promptly.

When to Call a Professional

Consider hiring a qualified painter if:

• You suspect asbestos in the fibrous cement — this is a job for licensed professionals.
• The soffit is high or difficult to access safely without scaffolding.
• There is significant structural damage or moisture ingress — this may involve a builder and could require a building consent depending on the scope of work (check with your local council).
• You're not confident in product selection or the prep work required.

A professional painter will have the right equipment, know the best products for your specific substrate, and back their work with a guarantee. You can find qualified local painters on tradedirectory.co.nz.

Sources & Further Reading

• WorkSafe NZ — Asbestos guidance
• James Hardie — Fibre cement technical information
• Resene — Exterior paint systems and primers
• Dulux NZ — Exterior painting guides
• BRANZ — Building research and best practice
• MBIE Building Performance — Consents and the Building Code