Articles
Your Spring Clean: Looking After Your Weatherboard Cladding
October 2026 - A little maintenance at the right time can help timber cladding continue to look and perform as intended. From knowing which changes are completely normal to spotting signs that need attention, this practical guide covers what to check, how to clean correctly, and when recoating may be needed.
Winter puts timber cladding through months of rain, wind, and low sun, and most of what it leaves behind sits quietly on the surface: dust, pollen, a bit of mould in the corners. None of it looks urgent. Left alone, it doesn't stay that way. Spring is when you walk the building, see what winter left behind, and deal with it properly.
Clean it when it needs it, and at least once a year
Wash your cladding whenever dirt, pollen, or organic matter builds up on the surface, rather than waiting for a set date. The annual inspection and clean is the longest you should go, covering walls, roofs, gutters, joinery, and walking areas together. In bush or high-pollen areas, and on coastal or geothermal sites, you'll be cleaning more often than that, and different elevations of the same house can need attention at different times.
The Walk-Around
What to look for
Most of what shows up on timber cladding is normal and not a sign anything's wrong. A few things are worth knowing on sight, because they tell you different things.
Silvering or greying
All timber turns grey or silver with UV exposure over time. It's a natural process, and it happens faster with clear or transparent coatings than with tinted ones. A clear coat does not stop this. If you're expecting a clear finish to hold its original colour indefinitely, it won't.
Fine surface cracks (checking)
Some timbers develop fine surface cracks after initial exposure. This is natural and isn't a problem on its own, as long as you keep up normal cleaning and recoating.
Black spots
Usually caused by airborne dust or pollen, sometimes from nearby site work like cutting fibre cement, brick, or concrete. A good quality exterior coating minimises them, and regular cleaning often fades them out over time.
Mould
Shows up where moisture lingers: sheltered or south-facing walls, spots with restricted airflow, or areas where vegetation is growing in too close. If you see it, that's your cue to clean and to check what's trapping the moisture there in the first place.
Cupping
Happens when heat and moisture levels differ significantly between the back of a board and its face. Worth a photo and a note if you spot it, so you can track whether it's getting worse.
If it looks like water is getting in
Damaged coating, failed sealant, or a lifted flashing needs fixing straight away, following the manufacturer's repair instructions for that part of the system. That's not a spring-clean job, that's a "deal with it now" job.
The Clean
How to actually clean it
The method matters more than the product. Timber cladding is not a driveway; it needs a gentler hand.
- Cut back vegetation growing too close to the cladding. It restricts airflow, holds moisture against the boards, and can scratch the surface.
- Pre-soak the surface before you start.
- Work in small sections, following the full length of each board top to bottom with back-and-forth strokes.
- Use a soft brush or car cleaning brush, mild detergent, and a standard hose.
- Go back over any areas that look discoloured or scratched, rather than leaving them to get worse.
Never use a water blaster
The pressure can leave visible marks or physical damage on the timber. This isn't a "use it carefully" caveat: water blasters should not be used on weatherboard cladding under any circumstances.
Location Matters
Not every wall weathers the same
Before you settle into a fixed maintenance schedule, it's worth understanding why one side of your house might need attention more often than another.
As a general cleaning guide: in a coastal environment, wash every 6 months; further from the coast, annually is enough.
Coming Up
Knowing when it's time to recoat
All coated timber cladding needs recoating at some point. How soon depends on how the original coating was applied and how exposed that part of the building is.
If you went with a tinted or pigmented finish, fading colour is your visual warning sign: it tells you when a recoat is due. Clear coatings don't give you that cue, which makes them harder to judge; the coating can wear away well before it's obvious to the eye. As a general guide, clear finishes, stains and water repellents often need recoating every 2 to 3 years, earlier than a painted finish.
Bubbling, flaking, or peeling on painted weatherboards should be dealt with immediately, not left for the next round of maintenance.
Before you recoat
Check with the coating manufacturer what preparation is needed, even if you're reapplying the same finish. Confirm the new coating is compatible with the original. And never coat over visible contaminants; it traps them underneath and makes the surface harder to clean from then on.
Using a JSC coating?
Always follow your coating manufacturer's own guidelines for preparation, application, and recoat timing, they take precedence over general advice like this. If your cladding is finished in JSC Scumble or JSC Coda.
One product worth being careful with: pure linseed oil encourages mould and fungal growth on timber cladding. Modern linseed oil-based products with biocides added are a different matter and don't carry the same risk, so check what's actually in the tin before ruling a product out.
If your fixings are silicone bronze, it's worth knowing they can cause visible copper leaching, more noticeable on lighter finishes. It's an aesthetic effect rather than a durability issue, but it's easier to plan around than to be surprised by.
Questions about your cladding?
If something doesn't look right, or you're not sure whether what you're seeing needs attention, JSC's technical team can help. Contact TechHelp@jsc.co.nz.
