A regular wash is one of the simplest, cheapest things you can do to extend the life of your Cedar. It’s also one of the most misunderstood, with homeowners either avoiding it altogether or approaching it the wrong way.
Done properly, washing protects your coating, keeps mould at bay, and pushes out the time between recoats. Here’s how to get it right, and when it’s worth calling in the professionals.
How Often Should You Wash?
If your Cedar isn’t due for a recoat, a light wash once a year is the general rule. It’s what we recommend to our own maintenance clients, and we’ll often suggest it ourselves when we check in on a property a year after coating.
Your environment matters too. Damp, bush-covered sections are more prone to mould, and coastal homes build up salt on the boards. Both benefit from washing more than once a year.
Cedar can be left for up to 4-6 weeks between washing and coating, at no detriment to the timber. If surface dust or pollen has landed on the Cedar in the interim, just brush it off before applying the coating.
Wash or Recoat? How to Tell
Look at the coating, not just what’s sitting on top of it.
Grime or early mould on top of an intact coating? Just wash it. Getting that build-up off stops it eating into the coating and helps it last longer.
Bare patches, or the coating looking worn and discoloured through to the timber? That’s exposed timber, and a wash alone won’t fix it. You’re looking at a recoat.
There’s no real situation where we’d tell you not to wash your Cedar. Even freshly coated boards can usually handle a wash within a month, once the oil has soaked in and the surface has dried. The real risk isn’t timing, it’s technique.
Light Wash vs Deep Clean
Not every wash needs the same amount of pressure. If the coating is in reasonable shape, a light wash paired with a recoat is usually enough. Where it’s broken down badly, or you’re dealing with bare, patchy timber, it needs a heavier wash to properly prepare the boards for coating.
Knowing which one a property needs takes experience, and it’s something we assess on site every time.
We do wash using low pressure water blasters, but the machine is the smallest part of the job. Our machines run at around 2,000 to 2,500 PSI, but by the time the water reaches the boards, from roughly a foot away and through a wide fan nozzle, the pressure hitting the timber is nowhere near that number.
The Technique That Keeps Cedar Safe
Cedar is soft, and it can be damaged by water pressure in the wrong hands. We train our technicians specifically in how to wash Cedar, and that training is a big part of what sets us apart from a general house washing company.
Three things matter most:
- A wide fan. We wash with roughly a 25-degree fan tip, spreading the pressure out rather than concentrating it on one spot.
- The right distance. Keep the spray about a board’s width from the surface, then adjust closer or further depending on how much clean the area needs.
- Never stop and go back. This is the biggest mistake people make. Pause mid-pass and go back over a spot, and you’ll leave a stop mark that’s hard to remove. Keep moving instead, fanning out at each end of your pass.
General upkeep and recoat prep also call for different approaches. For upkeep, you just want dirt and mould off the surface, without touching the coating underneath. For recoat prep, you can afford to take more of the old, oxidised tint off, since it’s all getting covered again.
Mixing the two up is where homeowners run into trouble: wash too close or too hard on boards that don’t need recoating, and you can strip enough tint to expose bare timber, creating a job that didn’t need to exist.
What We Use as a Surfactant
Before washing, we apply a surfactant, a biodegradable detergent mixed with water, sprayed onto the boards. It’s safe around plants and won’t damage windows, decks or joinery, so we don’t usually need to take any special precautions.
The one exception: on tank water properties, we isolate the water supply or disconnect the downpipes before washing above the roofline, so nothing runs into the drinking water.
We leave the surfactant on for three to five minutes minimum, ideally still wet when we come to wash it off, mixing it stronger for particularly dirty properties.
Once washed, the timber needs to dry completely before oiling. Cedar is light and dries fast, sometimes within an hour or two on a sunny north face. We generally wash one day and coat the next, though same-day turnarounds aren’t unusual in summer.
What Incorrect Washing Looks Like
At the mild end, poor preparation means not enough of the old coating has come off for a fresh coat to bond properly. At the more serious end, you get actual gouges or scarring in the timber, or the stop marks mentioned above.
Some of this can be fixed. Badly scored timber usually can’t be. Sanding it back just leaves a fainter impression of the same mark, since you’re left with a flat board and an indentation in it.
This is why we’re cautious about recommending homeowners attempt heavier prep washes themselves, even though a light annual rinse is well within most people’s ability.
Should You Wash It Yourself?
If you’re comfortable doing it, an annual clean is a job you can happily take on yourself.
Before a recoat, we’d always recommend a specialist. Preparing Cedar properly is a different skill set to a standard house wash, and it’s exactly what we specialise in. General house washing companies tend to steer clear of Cedar for this reason.
Final Thoughts
A regular wash does more than keep your Cedar looking tidy. On shaded, damp faces where mould takes hold, it protects the coating underneath and helps it last as long as possible.
Sun-exposed north faces are a different story. They take the brunt of New Zealand’s UV and need recoating every 2-3 summers regardless of how well they’re washed, since it’s the sun doing the damage there, not the dirt.
Not sure whether your Cedar needs a wash or something more? Our Free Cedar Assessment will give you a clear, honest answer either way.
