Why Weatherboard Is Different
Timber isn't static. Every day the sun warms weatherboard and it expands slightly; overnight it cools and contracts. Add rain, dew and humidity, and the boards take on and release moisture as well. A paint film has to cope with all of that movement, year after year.
New paint is flexible enough to do it. Old paint isn't. Over time it becomes harder and more brittle, and eventually develops hairline cracks you can barely see. Those cracks let moisture in, and that moisture weakens the paint's hold on the timber underneath. Almost every weatherboard problem comes back to that cycle.
The Six Issues That Catch Weatherboard Owners Out
1. Moisture already inside the timber. Paint can only stay bonded to timber that's dry. Dulux's technical guidance gives a clear rule of thumb: if bare timber is holding more than about 15% moisture, it isn't ready to be painted and needs to dry out first. Paint applied over damp timber seals the moisture in, and the next sunny day pushes it back out through the paint film.
2. Blistering. Those bubbles are the paint film lifting where it has lost adhesion. Dulux describes two main causes: moisture trapped beneath the paint that turns to vapour and expands in the sun, and solvent trapped during application when the surface heats up too quickly. Blistering is often worst on walls facing north and west, where the sun does the most work. A telltale sign is blisters that shrink in the cool of the evening and reappear the next warm day. Patching individual blisters rarely fixes it, because blistering means the paint's grip is failing more broadly, and more blisters usually follow.
3. Old paint that has quietly lost its grip. A wall can look fine and still have paint that's no longer properly bonded, very often at the bottom layer where the original primer meets the timber. Fresh coats over unsound paint just carry the weakness upward. Dulux's guidance is to test how sound the existing paint really is, using simple cross-hatch adhesion tests on a clean area, and where it isn't sound, to strip it back to a firm surface before repainting.
4. Bare or weathered timber. Exposed timber deteriorates surprisingly quickly. It can turn grey and become unsuitable for painting in as little as three months. The weathered surface has to be taken back to fresh timber, either by sanding or with a timber reviver treatment, before primer and paint go on. Skip that and the paint is bonding to a layer that's already breaking down.
5. Dark colours on sun-facing walls. Dark colours absorb more heat, which means more expansion and contraction in the boards and more stress on the paint system. It doesn't mean you can't choose one, but it's a genuine trade-off, especially on north and west walls. It's also why dark exterior colours are treated differently under our terms and conditions, and why we'd rather talk it through at the estimate than have you find out later.
6. Worn joints, nail holes and rot. Weatherboard has a lot of joints, laps and fixings, and each one is a potential way in for water. Nail holes and gaps need filling with the right material, and boards that have started to rot need dealing with, not painting over. If we find damage like this during preparation, we'll always stop and talk it through with you first, since it may involve costs outside the original quote.
Where Your Home Sits Makes a Difference
Two identical weatherboard homes can age very differently depending on where they are. Walls that take the most direct sun, particularly north and west, wear fastest, and homes in exposed coastal spots such as Sumner deal with extra wind and salt. Even shade matters: a damp, sheltered south wall can hold moisture longer and grow mould more readily. None of this is a problem in itself, but it's why a good assessment looks at each side of the house separately, rather than treating the whole home the same.
Read Your Own Walls: What to Look for Now
A short walk around your home is enough to spot most early warning signs:
- Bubbles or blisters, especially on north- and west-facing walls (late on a sunny afternoon is the best time to look)
- Paint lifting, flaking or peeling at board edges and joints
- A chalky residue that rubs off on your hand
- Grey, bare or rough-looking timber, particularly on lower boards and around windows
- Hairline cracks along boards or at joints
- Soft or spongy patches when you press the timber gently
- Dark staining or mould that returns quickly after washing
Finding one or two of these isn't cause for alarm. It's a prompt to get the walls properly assessed. Our guide to signs your paint needs attention explains which ones are cosmetic and which aren't.
What a Proper Weatherboard Repaint Involves
The issues above are exactly why preparation gets more attention than the paint itself. On a weatherboard home, a properly done repaint follows this sequence:
- Protect the property. Plants, decks, outdoor furniture and non-painted surfaces are covered before any work starts.
- Wash. All exterior surfaces are power washed with Dulux House Wash to remove dirt, mould and chalking.
- Sand and remove loose paint. Flaking and peeling paint is taken back so the new coating has something sound to bond to.
- Fill and repair. Cracks and nail holes are filled with the right material for the surface, whether gap filler, timber filler or putty, then sanded smooth.
- Prime. Bare and repaired areas are primed with the correct undercoat for the timber.
- Paint. A minimum of two coats of Dulux Weathershield, formulated for strong sun protection and resistance to colour fading, and self-priming on most surfaces.
- Clean up and hand over. Work areas are cleaned up daily and on completion, and we walk the finished result through with you before calling it done. Labelled containers of your final-coat paint are left with you for future touch-ups.
Every project is backed by the Master Painters NZ 5-Year Guarantee, covering surface preparation and coating applied to the AS/NZS 2311 standard. Like any guarantee it has terms, including how dark exterior colours are treated, and we're happy to walk you through them. For more on why each step matters, see The Importance of Surface Preparation.
Why Early Planning Pays Off
Exterior painting depends on the weather. Preparation and paint both need suitable conditions, and Canterbury's weather can swing a lot between seasons and even between days. There's a real advantage in having your assessment, colour decision and booking sorted before settled weather arrives, rather than after. We cover the conditions that matter in The Perfect Temperature for Exterior Painting.
Timber also doesn't wait. If moisture, blistering or weathering is already underway, it's better to know now, so repairs can be planned into the project and boards given time to dry if they need it. As a guide, most exterior projects take between 5 and 10 days. A single-storey home is often 4 to 6 days and a large two-storey home 7 to 10, with the weather having the final say. If conditions aren't right on a scheduled day, we'll reschedule rather than push ahead, and keep you informed.
What Weatherboard Painting Costs
Weatherboard pricing depends on size, condition and access. As a guide from our current pricing:
House type | Typical preparation / access needs | Average NZD range |
|---|
Medium weatherboard (single storey) | Pressure wash, sanding, minor weatherboard repair, short-term scaffolding | $12,300 – $18,900 |
Large two-storey, cedar stain | Light pressure wash, stain weatherboard, short-term scaffolding | $9,000 – $13,800 |
Two things move these numbers most: the condition of the existing paint and timber (more repair and preparation means more time) and access (a two-storey home needs short-term scaffolding). Every property is different, so the only reliable figure is a written estimate after a proper look. Our Exterior Painting Cost Guide covers the other cladding types too.
Questions to Ask Any Painter About Your Weatherboard Home
Whoever you choose, these questions separate a quick repaint from a lasting one:
- How will you check the existing paint and timber are sound before painting?
- What preparation is included (washing, sanding, filling, priming) and is it all in the quote?
- What happens if you find rot or damage once work starts, and who decides what happens next?
- What paint are you using, and is it suitable for full sun exposure?
- How do you approach dark colours on north- and west-facing walls?
- What does the guarantee actually cover, and who stands behind it?
- What happens if the weather turns mid-project?
Feel free to pass this page on to anyone comparing quotes.
