Painting a wooden deck that has previously been oiled is absolutely achievable as a DIY project, but the key to success is thorough preparation. Oil and paint don't bond well together, so if you skip the prep steps, your new paint coat will peel within a season. Follow the process below and you'll end up with a durable, great-looking deck finish.
Why Oiled Decks Need Special Preparation
Deck oils penetrate the timber and leave a residue on the surface that repels water-based and many solvent-based coatings. Applying paint directly over oil will cause poor adhesion, bubbling, and premature peeling. The goal of preparation is to remove as much residual oil as possible and create a surface the paint can grip.
What You'll Need
- Stiff-bristle deck scrubbing brush
- Deck cleaner or degreaser (sugar soap or a dedicated timber cleaner)
- Pressure washer or garden hose
- Orbital or belt sander with 60–80 grit sandpaper
- Pole sander for flat areas
- Tack cloths or clean rags
- Appropriate primer
- Deck paint or solid colour deck stain
- Paintbrush, roller, and/or pad applicator
- Safety glasses, dust mask (P2 rated), and knee pads
Step 1 – Clean the Deck Thoroughly
Start by sweeping away all loose debris. Mix a deck cleaner or sugar soap solution and scrub the entire surface with a stiff brush, working it well into the grain. This lifts surface oil, dirt, mould, and mildew. Rinse thoroughly with a pressure washer or hose and allow the deck to dry completely — in most NZ conditions this means at least 48–72 hours of dry weather. Moisture trapped under paint is one of the most common causes of failure.
Step 2 – Sand the Surface
This is the most important step. Sanding removes the oil-saturated top layer of timber and gives the paint a mechanical key to grip. Use 60–80 grit sandpaper on an orbital or belt sander, working along the grain. Pay extra attention to areas that look darker or feel tacky — these have higher oil saturation. After sanding, wipe down with tack cloths or a clean dry rag to remove all dust. Do not use a damp cloth at this stage.
Safety note: If your deck was built before the mid-2000s and treated with CCA (copper chrome arsenate) timber preservative, sanding can release hazardous dust. Check with WorkSafe NZ for guidance on safe handling, and always wear a P2 dust mask when sanding any older timber.
Step 3 – Check for Remaining Oil
Sprinkle a few drops of water on the sanded surface. If the water beads up, there is still oil present and you need to sand further or apply a second round of degreaser and rinse. If the water soaks in readily, you're good to move on.
Step 4 – Apply a Suitable Primer
Primer is non-negotiable when painting over a previously oiled surface. Choose a penetrating oil-based or shellac-based primer that is specifically recommended for previously oiled or difficult-to-coat timber. Check the technical data sheet of your chosen topcoat and use the primer recommended by the same manufacturer to ensure compatibility.
Resene and Dulux both offer timber primers suitable for exterior decking — visit their websites or speak to an in-store consultant to confirm the right product for your situation. Apply primer according to the manufacturer's instructions and allow it to cure fully before topcoating.
Step 5 – Apply Your Deck Paint
Choose a purpose-formulated exterior deck paint or solid colour deck coating — these are designed to handle foot traffic, UV exposure, and the wet-dry cycles common in NZ's varied climate. Avoid standard exterior wall paint, which won't hold up underfoot.
Apply in thin, even coats, working along the length of the boards. Two coats are typically recommended. Check the recoat window on the tin and don't rush between coats. Avoid painting in direct hot sun or when rain is forecast within 24 hours.
Wattyl also produces exterior deck coatings worth considering. Products are available from Bunnings, Mitre 10, and PlaceMakers.
Choosing the Right Conditions
NZ weather varies enormously by region. As a general guide:
- Paint when temperatures are between 10°C and 30°C
- Relative humidity should be below 85%
- Avoid painting in direct midday sun — the surface can skin over before the paint penetrates
- Spring and early autumn are often ideal in most NZ regions
Maintenance Going Forward
Once you've switched from oil to paint, stick with paint for future maintenance coats. Reapplying oil over paint will cause the same adhesion problems in reverse. Lightly sand between maintenance coats and clean the surface before recoating every few years, or as the manufacturer recommends.
When to Call a Professional
Deck painting is generally DIY-friendly, but consider hiring a qualified painter if:
- Your deck is large, multi-level, or hard to access safely
- The timber is in poor condition with rot, significant cracking, or raised grain that needs professional assessment
- You're unsure about the previous coating or timber treatment
- You want a guaranteed, high-quality result
Painting is not restricted trade work under NZ law, but a professional will have the right equipment, product knowledge, and experience to get the best outcome. You can find qualified local painters on tradedirectory.co.nz.
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