How to Sand Back and Repaint Timber Joinery: The Best Method

Sanding back and repainting timber joinery — windows, doors, architraves, and skirting boards — is one of the most rewarding DIY projects a homeowner can tackle. Done properly, a fresh coat of paint protects the timber from moisture and UV damage and can add years to the life of your joinery. The key is thorough preparation: rushing the sanding and priming stages is the most common reason repaint jobs fail early.

Gather Your Tools and Materials

Before you start, get everything together so you're not stopping mid-job. You'll need:

• Sandpaper in a range of grits (80, 120, and 180–240 for finishing)
• A sanding block or random orbital sander for flat sections
• Detail sander or folded sandpaper for mouldings and rebates
• Sugar soap or a degreasing cleaner
• Painter's tape and drop sheets
• Flexible filler or wood filler for cracks and gaps
• Primer suitable for timber
• Topcoat paint — waterborne or oil-based, depending on your preference
• Quality brushes (a 50–75 mm angled sash brush works well for joinery)

You'll find most of these at Bunnings or Mitre 10.

Check for Lead Paint First

If your home was built before 1980, there is a real chance your existing joinery paint contains lead. Sanding lead paint creates hazardous dust. Before you start, pick up an inexpensive lead paint test kit (available at hardware stores) or have the paint tested professionally. If lead is present, you must take precautions — wear a P2 respirator, contain the dust, and dispose of waste carefully. Check WorkSafe NZ for guidance on working safely with lead paint.

Prepare the Surface Thoroughly

Good preparation is 80% of the job.

1. Clean the joinery with sugar soap and warm water to remove grease, grime, and mould. Rinse and allow to dry completely — damp timber will cause paint to blister and peel.
2. Sand back the existing paint starting with 80-grit to remove flaking, peeling, or heavily chalked paint. Work with the grain of the timber. You don't need to strip back to bare wood everywhere — just ensure all loose or failing paint is removed and edges are feathered smooth.
3. Move to finer grits (120, then 180–240) to smooth the surface and key it for the new primer.
4. Fill any cracks, splits, or nail holes with a flexible exterior-grade filler for outside joinery, or a standard interior wood filler for inside. Allow to cure fully, then sand flush.
5. Wipe down with a tack cloth or damp rag to remove all dust before priming.

Prime Before You Paint

Never skip the primer — it seals the timber, improves adhesion, and helps the topcoat last far longer. For bare or heavily sanded timber, use a dedicated timber primer. If you're painting over sound existing paint, a bonding primer or undercoat may be sufficient.

Leading NZ paint brands including Resene, Dulux, and Wattyl all offer timber primers suited to both interior and exterior joinery — check their websites or ask in-store for the right product for your situation. Always follow the manufacturer's recoat times.

Apply the Topcoat

Once the primer is fully dry and lightly sanded with 240-grit, you're ready to paint.

• Apply two topcoats for best coverage and durability, lightly sanding between coats with 240-grit and wiping clean.
• Use a semi-gloss or gloss finish for joinery — these are easier to clean and more moisture-resistant than flat or low-sheen paints.
• Waterborne (acrylic) paints are easier to clean up and dry faster; oil-based paints are harder and more durable but take longer to dry and require solvent for clean-up. Both can work well on joinery.
• Paint in the direction of the timber grain and avoid overloading the brush to prevent runs.
• For exterior joinery, ensure the paint system meets the demands of your local climate — coastal and high-UV areas need robust, UV-resistant topcoats.

Tips for a Neat Finish

• Tape up glass carefully with painter's tape to get a clean line on window frames.
• Remove door hardware (handles, hinges) where possible rather than painting around them.
• Paint doors in sections: panels first, then rails, then stiles.
• Allow adequate drying time before closing doors or windows — especially in humid or cold conditions.

When to Call a Professional

While repainting joinery is a manageable DIY project, there are times when it pays to bring in a qualified tradesperson:

• Lead paint is confirmed and you're not confident managing the hazard safely.
• The timber itself is rotted or damaged — a joiner will need to repair or replace sections before painting.
• You want a spray-applied finish for a factory-smooth result.
• The job is large, complex, or involves heritage joinery requiring specialist knowledge.

A qualified painter or joiner will get the job done efficiently and with a guaranteed result. You can find experienced local tradespeople on tradedirectory.co.nz.

Sources & Further Reading

• Resene — Paint application guides and product selector
• Dulux NZ — Painting timber joinery advice
• WorkSafe NZ — Lead paint safety
• BRANZ — Building research and best practice
• Bunnings NZ — Tools and painting supplies
• Mitre 10 NZ — Painting and decorating products