How to Prepare Your Home for Exterior Painting

Exterior painting is one of the most cost-effective ways to protect and refresh your home, but the quality of the finish depends almost entirely on how well you prepare the surface beforehand. New Zealand's climate — high UV in the north, driving rain on the West Coast, salt air in coastal areas, and hard frosts in the South Island — puts painted surfaces under serious stress. Getting the preparation right means your paint job will last years longer and look far better.

Why Preparation Matters More Than the Paint

Even the best exterior paint will fail prematurely if it's applied over a poorly prepared surface. Adhesion is everything. Paint applied over dirty, chalky, cracked, or damp surfaces will peel, bubble, and blister — often within a season. Professional painters routinely say that preparation accounts for 70–80% of the total job effort, and that's not an exaggeration.

NZ's high UV levels (particularly in the upper North Island) accelerate paint breakdown, while coastal salt spray and high humidity in places like Northland, the Coromandel, and Fiordland can cause rapid corrosion on metal surfaces and moisture ingress behind paint films.

Step-by-Step Preparation Process

1. Inspect the Entire Exterior

Before you touch a brush or a pressure washer, do a thorough inspection. Walk around the house and look for:

• Peeling or flaking paint — indicates moisture behind the film or poor adhesion from the last job
• Chalking — a powdery residue on older paint surfaces, common on weatherboards
• Cracks and gaps in weatherboards, around window and door frames, and at junctions
• Rot or damage in timber — probe with a screwdriver; soft spots need repair before painting
• Rust stains on or around metal fixings, flashings, or joinery
• Mould and mildew — very common in shaded, damp areas of NZ homes
• Previous paint type — oil-based and water-based paints require different primers

If your home was built before 1980, there is a real possibility that existing paint contains lead. Do not sand or water-blast lead paint without appropriate precautions. Check WorkSafe NZ for guidance on working safely with lead paint.

2. Clean the Surface Thoroughly

All exterior surfaces must be clean before any paint is applied. The standard approach in NZ is:

• Water-blast (pressure wash) the entire exterior to remove dirt, cobwebs, loose paint, and surface contamination. Use a fan tip and keep the nozzle moving to avoid gouging timber.
• Treat mould and mildew with a suitable fungicidal wash. Many NZ painters use a diluted bleach solution or a proprietary product. Allow adequate dwell time, then rinse thoroughly.
• Allow the surface to dry completely — this is critical. Painting over damp timber is one of the most common causes of paint failure in NZ. In cooler or wetter regions, allow several dry days before proceeding.

3. Repair Damaged Surfaces

Once clean and dry, carry out all repairs:

• Fill cracks and gaps with an appropriate flexible exterior filler or paintable sealant. Around windows and doors, use a good-quality polyurethane or acrylic sealant that can flex with seasonal movement.
• Replace rotted timber sections. Do not paint over rot — it will continue to spread beneath the film.
• Treat bare timber with a timber preservative where appropriate, particularly in high-moisture areas.
• Sand all repaired areas smooth and feather the edges of any remaining old paint to avoid visible ridges in the new finish.
• Prime all bare timber, repaired areas, and any bare metal before topcoating. Skipping primer on bare surfaces is a false economy.

4. Mask and Protect

Before painting begins, protect everything you don't want painted:

• Mask windows, doors, and trim with painter's tape and plastic sheeting
• Cover paths, decks, and garden beds with drop sheets
• Remove or mask light fittings, letterboxes, and downpipe brackets where practical

Choosing the Right Products for NZ Conditions

NZ's climate demands paints and primers specifically formulated for local conditions. Key considerations:

Well-regarded NZ paint brands include Resene, Dulux, and Wattyl. All three offer exterior systems designed for NZ conditions and provide technical data sheets to help you choose the right product for your substrate and region. Your local Resene ColorShop or Dulux trade rep can advise on the best system for your specific situation.

For fibre cement cladding such as James Hardie products, always follow the manufacturer's painting specifications — James Hardie publish these on their website and warranty compliance depends on using approved systems.

Building Consent and Compliance

In most cases, repainting an existing exterior does not require a building consent — it is considered maintenance. However, there are situations where consent may be needed:

• Changing the cladding type or adding new cladding
• Repairing significant areas of cladding that affect weathertightness
• Any structural repairs associated with the painting project

Always confirm with your local council before starting work if you are unsure. The MBIE Building Performance website has clear guidance on Schedule 1 exemptions and when consent is required.

If your home is a rental property, note that the Healthy Homes standards require rental properties to be free from dampness and mould — addressing these issues before painting is not just good practice, it may be a legal obligation.

DIY vs Hiring a Professional

Many NZ homeowners tackle exterior painting themselves, and it is certainly achievable on a single-storey home with good preparation. However, consider hiring a professional if:

• Your home is two or more storeys (working at height carries serious risk — see WorkSafe NZ)
• There is significant rot, weathertightness damage, or lead paint present
• You want a warranty-backed result
• The cladding is a specialist product with specific application requirements

Always get multiple quotes from qualified tradespeople, check their references, and ask to see examples of previous work. A good painter will carry out their own thorough inspection before quoting and will include preparation in their scope of work — be wary of quotes that seem to skip this step.

When to Call a Professional

Call a qualified painter or building trades professional when:

• Lead paint is present or suspected — disturbing lead paint without proper controls is a health and safety risk
• Significant rot or structural damage is found — this may require a Licensed Building Practitioner (LBP); check LBP
• Working at height above one storey
• Weathertightness issues are identified — these need proper diagnosis and repair, not just a coat of paint
• You want the manufacturer's paint warranty to be valid — some warranties require professional application

You can find qualified local painters and building tradespeople on tradedirectory.co.nz.

Practical Tips for Getting Good Value

• Plan your project budget carefully and include a contingency — repairs discovered during preparation can add to costs
• Time your project well — exterior painting in NZ is best done in dry, mild weather. Avoid painting in direct hot sun, high winds, or when rain is forecast within 24 hours
• Use quality materials suited to NZ conditions — cheaper paint may cost more in the long run through early failure
• Get written quotes that clearly specify the preparation work included, the products to be used, and the number of coats

Sources & Further Reading

• MBIE Building Performance — Building Consent information
• WorkSafe NZ — Working safely with lead paint and at height
• Resene — Exterior paint systems and technical advice
• James Hardie — Fibre cement painting specifications
• BRANZ — Building research and best practice guidance
• Tenancy Services — Healthy Homes standards