Window frames and sills cop a hard beating in the New Zealand climate — UV, rain, humidity, and temperature swings all take their toll. Done properly, a fresh coat of paint not only looks great but also protects the timber or aluminium underneath from rot and moisture damage. Here's how to get a professional result, whether you're refreshing the interior or tackling the exterior.
Assess the Condition First
Before you open a tin, take a close look at what you're working with. Check for:
- Peeling or flaking paint — a sign of moisture getting underneath
- Rot or soft spots in timber frames (press with a screwdriver; if it sinks in, you have rot)
- Gaps or failed sealant around the frame where water can enter
- Mould or mildew, especially on south-facing or shaded windows
If you find significant rot, you'll need to repair or replace the affected timber before painting. Small areas can be filled with a two-part epoxy wood filler; larger sections may need a joiner or carpenter. Addressing moisture issues first is critical — paint alone won't fix an underlying problem.
Gather Your Materials
Having the right gear on hand makes the job much smoother. You'll need:
- Sandpaper (80–120 grit for cutting back, 180–220 grit for finishing)
- Sugar soap or a mild detergent for cleaning
- Painter's masking tape (low-tack for glass)
- Quality primer suited to your surface
- Topcoat paint (see below)
- Angled sash brush (25–50 mm) — essential for neat lines on frames
- Putty knife or scraper for removing loose paint
- Flexible exterior sealant (for gaps around the frame)
Preparation: The Most Important Step
Professional painters will tell you that prep is 80% of the job. Skipping it is the number-one reason paint fails prematurely.
- Clean the surface thoroughly with sugar soap and water, then rinse and allow to dry completely.
- Scrape and sand all loose, flaking, or peeling paint back to a firm edge. Feather the edges so there's no hard ridge.
- Fill any holes or cracks with a suitable exterior filler or timber putty. Allow to cure, then sand smooth.
- Re-seal gaps between the frame and the wall with a paintable flexible sealant. This is especially important for exterior windows under the NZ Building Code requirements around weathertightness.
- Mask the glass carefully with low-tack tape, leaving a 1–2 mm overlap onto the glass — this creates a weather seal when the paint dries.
Safety note: Homes built before the 1980s may have lead-based paint on window frames. If you suspect lead paint, use wet sanding methods, wear a P2 respirator, and check WorkSafe NZ guidance before proceeding.
Choosing the Right Paint
The paint you choose matters enormously, particularly for exterior sills which sit horizontal and pool water.
| Surface | Recommended Paint Type | Key Properties |
|---|---|---|
| Exterior timber frames | Waterborne or oil-based trim enamel | UV resistance, flexibility, hard-wearing |
| Exterior sills | High-gloss or semi-gloss exterior enamel | Water run-off, durability |
| Interior timber frames | Waterborne trim enamel or acrylic | Low VOC, easy clean-up |
| Aluminium frames | Adhesion primer + acrylic topcoat | Bonding to non-porous surface |
Resene and Dulux both offer excellent trim and enamel ranges well suited to NZ conditions. Wattyl is another trusted option widely available at hardware stores. For exterior sills especially, choose a gloss or semi-gloss finish — it sheds water more effectively than flat or low-sheen paints.
Priming: Don't Skip It
A good primer is the foundation of a lasting paint job:
- Bare or repaired timber always needs a primer coat before topcoats.
- Aluminium frames need a dedicated etch primer or adhesion primer — standard paint won't bond well to bare aluminium without it.
- Previously painted surfaces in good condition can often be lightly sanded and topcoated, but a primer coat is still recommended if you've done significant sanding or repairs.
Allow the primer to dry fully (check the tin for recoat times) before applying your topcoat.
Painting Technique for a Neat Finish
- Use a quality angled sash brush — cheap brushes leave brush marks and shed bristles.
- Paint the rebate first (the part that touches the window sash), then work outward to the face of the frame.
- Apply thin, even coats rather than one thick coat. Two coats of topcoat is standard; three is better for exterior sills.
- Maintain a wet edge — work quickly enough that you're always brushing into wet paint to avoid lap marks.
- On sills, finish strokes in the direction of water run-off (front to back, toward the drip edge).
- Allow full drying time between coats as specified on the tin. Rushing this is a common mistake.
- Remove masking tape while the final coat is still slightly tacky for the cleanest edge.
Exterior vs Interior: Key Differences
Exterior windows face far harsher conditions. Use exterior-rated paints only, ensure all gaps are sealed, and aim to paint on a dry day with mild temperatures (generally 10–25°C). Avoid painting in direct hot sun, which causes the paint to dry too fast and can lead to blistering.
Interior frames are more forgiving, but in wet areas like bathrooms, choose a mould-resistant paint formulation and ensure good ventilation — relevant to Healthy Homes standards for rental properties.
When to Call a Professional
Consider hiring a qualified painter if:
- You have multiple windows or a two-storey home requiring scaffolding or ladders at height
- There is significant rot, weathertightness failure, or structural issues
- You suspect lead paint and aren't confident managing the hazard safely
- You want a guaranteed, long-lasting result — a professional will carry the right insurance and know-how
A qualified local painter can be found easily on tradedirectory.co.nz. Painting is not licensed restricted work in NZ, but a skilled tradesperson brings experience, quality materials, and efficiency that's hard to match on a DIY basis.