Cladding · Timber weatherboard
Weatherboard is the forgiving cladding. That is exactly why it gets neglected.
Timber weatherboard barely featured in New Zealand’s weathertightness failures. It breathes, it dries, and when a board does rot you can cut it out and replace it. The trade-off is that the paint film is doing real protective work — so on weatherboard, preparation is not the part you can save money on.
2%
Estimated weathertightness failure rate for weatherboard cladding, against 95% for monolithic and stucco. National estimates for the 1992–2005 build period.
Three timbers, three problems
Kauri, cedar, pine
Old-growth kauri and rimu (roughly pre-1940)
Dense, tight-grained, dimensionally stable, and often in better condition under the paint than the paint itself suggests. It holds a fastener, takes a scarf repair cleanly, and is worth saving — replacement boards in matching profile are milled to order and are not cheap. The problem on kauri villas is almost never the timber. It is eighty years of accumulated coatings, the lowest layers of which are very likely lead-based.
Western red cedar (common on 1960s–1990s houses)
Light, stable, naturally durable, and full of water-soluble extractives that bleed through a waterborne coating as brown staining. It needs a stain-blocking primer, and any previous oil or stain has to come off first. Cedar in bevel-back or board-and-batten form also moves at the fixings, so the fastener heads and the batten edges are where the film opens up first.
Treated radiata pine (most post-1980 weatherboard)
Fast-grown, softer, and much more sensitive to moisture cycling. It cups, the grain raises, and the butt-joints open. Pine boards also carry factory primer that has often been exposed for far longer than the manufacturer intended before the first topcoat went on — and an over-exposed primer must be sanded and re-primed, not painted over.
BRANZ Study Report SR456, “Assessing the condition of New Zealand housing” · 2020
Health and safety, said plainly
Lead paint on pre-1980 houses
This is not a footnote. It is the one part of repainting an older Auckland house that can genuinely harm the people living in it, and it is routinely ignored.
Lead compounds were used as pigment and drier in New Zealand house paint for most of the twentieth century and were not gone from domestic paint until the 1980s. On a pre-1980 house, assume the lower coats contain lead unless a test says they do not. Test swabs are inexpensive and sold at trade paint suppliers; a laboratory test on a paint chip is definitive.
An intact, painted-over lead film is not the hazard. The hazard is the dust and the chips, and the three things that create them are dry sanding, aggressive scraping, and heat-gun or open-flame stripping — heat is the worst of the three because it puts lead into the air you are breathing. The dust then settles in the soil under the wall and in the ceiling space, and stays there.
The people most at risk are children under six and pregnant women, because lead does its damage to developing nervous systems at concentrations that produce no symptoms in an adult. If there are young children in the house or next door, this changes how the job should be run — wet methods, sheeting to catch chips, HEPA vacuum rather than a broom, sandpit and vegetable garden covered, and washing before anyone comes back inside.
WorkSafe New Zealand publishes the control requirements for lead-based paint removal, and a painter working on villas should already be operating to them. Ask. If the answer is vague, that tells you something about the rest of the job.
The specification
A three-coat weatherboard system, in order
Nothing exotic. What separates a job that lasts from one that does not is whether each of these steps was actually done, and whether the wall was dry enough when the paint went on.
- 01
Wash and kill the biological growth
Auckland’s humidity means moss, mould and lichen on any shaded or south-facing elevation. A wash alone removes the visible growth and leaves the spores. Treat, dwell, rinse.
- 02
Cut out and replace what has gone
Rotten board ends, split scribers, failed corner moulds, perished putty in timber-sashed windows. A scarf repair in matching profile, glued and fixed, is the right answer on kauri. Filler in a rotten board end is not a repair, it is a delay.
- 03
Sand back the failed film and feather the edges
Wet-sand or use dust-extracted sanding on anything pre-1980. The aim is a sound, keyed, continuous surface — not bare timber everywhere.
- 04
Check the moisture content
A pin meter in the timber, on the south wall and at the bottom edges, before priming. Under about 18%. This is the step that gets skipped when a crew is behind schedule, and it is the one that causes blistering six months later.
- 05
Prime for what is underneath
Bare timber gets an oil-based or waterborne wood primer. Cedar gets a stain blocker. Chalky old acrylic gets a bonding sealer. Old enamel gets de-glossing plus an adhesion primer. Knots and resin bleed get spot-sealed regardless.
- 06
Re-seal the joints, then two topcoats
Flexible sealant at the scribers, corners and window junctions after priming and before the topcoats, so it bonds to primer rather than to old paint. Then two full topcoats at the stated spreading rate — the quantity calculator shows what that actually means in litres.
Questions people actually ask
How often does weatherboard need repainting in Auckland?
Judgement, not data: on a well-prepared three-coat acrylic system, six to ten years on sheltered elevations and five to eight on the weather side. Auckland’s north and west elevations take the ultraviolet load and fail first, which is why one wall often looks a decade older than the rest of the house. The honest test is not the calendar — it is whether the film is chalking when you rub it, and whether the caulking at the joints has gone hard.
Can you paint over old oil-based paint on weatherboard?
Yes, but not directly. Old enamel is hard and glossy, and a waterborne topcoat will not key to it. It needs to be de-glossed by sanding and then sealed with an adhesion-promoting primer rated for the transition. Skip that step and the new paint peels in sheets in about two years, usually taking the old coating with it.
Does the paint need stripping back to bare timber?
Usually not, and doing it unnecessarily is expensive. Strip where the film has failed — where it is flaking, blistering or has lost adhesion — then feather the edges so the repair does not telegraph through. Full strip is warranted when there are so many layers that the profile has lost definition, or when the existing build-up is cracking through every coat at once.
Is lead paint really a problem on my old villa?
It is a genuine one. Lead was used in New Zealand house paint for decades and was not fully out of domestic paint until the 1980s, so on a pre-1980 house you should assume the lower layers contain it until a test says otherwise. The hazard is not the intact film — it is the dust and chips created by dry sanding, scraping and heat-gun stripping, and the risk falls hardest on young children and on pregnant women. Test kits are sold at trade paint suppliers. WorkSafe New Zealand publishes the control requirements, and any painter working on an older house should already know them.
What about cedar? It looks different when it is repainted.
Cedar is the substrate that punishes shortcuts. It is naturally durable and does not need paint to survive, but its water-soluble tannins bleed through waterborne coatings as brown staining, especially where the board has been left bare or washed hard. It needs a stain-blocking primer, and previously oiled or stained cedar needs the residue removed before anything is applied. Painting cedar is also a one-way decision in practice: getting back to an oiled finish afterwards means stripping, and it never quite looks the same.
How wet is too wet to paint timber?
The trade rule of thumb is under about 18% moisture content, measured with a pin meter in the timber itself, not judged by touch. Paint applied over timber above that traps water behind the film, and the film then blisters from the inside out. After a wet Auckland week, a south-facing weatherboard wall can still be over the line three days later — which is the real reason winter exteriors go wrong.
Next
If your house is weatherboard at the front and plaster at the back — very common on Auckland houses with a 1990s addition — read the plaster page as well, because that elevation is the one that decides the programme. The Auckland climate model shows how many days a month actually meet the application limits, which is what determines when this work can be booked.