Look, we get it. You opted for composite decking because you were convinced that it was “maintenance-free”. And while that's largely true in contrast to timber, it's not like you can forget about your deck altogether. The best composite needs some TLC to maintain its looks.

Our Perth climate is a tough one; our incessant sun, sporadic heavy rain and that dusty stuff just lying around make for some wearisome conditions on your deck year in, year out.

No matter whether you have Trex or Millboard, reading the rest of this article will ensure it is clean for many years to come.

So, let’s take a closer look at the essential details of composite deck cleaning that Perth homeowners need to know.

Why Bother Cleaning Composite Decking?

Fair question. After all, you didn’t choose composite decking with the intention of scrubbing it every weekend, did you?

After all, while composite decking is designed to resist rotting and warping due to its weather-resistant nature, it can still become dirty and stained with leaves. Perth's climate is particularly challenging.

According to the Australian Bureau of Meteorology, "we can experience UV index levels of 11-12 in the summer." The Washington Department of Health says this is a perfect scenario for the growth of mould spores.

Mould can cause respiratory symptoms, particularly in asthma and allergy sufferers, health authorities warn. Routine sanitation helps keep spore counts in check.

And most composite decking warranties can be voided if you don’t maintain it according to the manufacturer’s instructions. Nobody wants that.

The Basics: What You'll Need

Before I give you brand-specific advice, let’s talk about your cleaning arsenal.

Here’s what works for most composite decking:

A good broom (stiff bristles work best)
Garden hose with spray nozzle
Soft-bristle brush or deck brush
Bucket
Gentle dish soap or specific composite deck cleaner
White vinegar (your secret weapon)
Baking soda for stubborn stains

Hmm, and what is not on that list? Aggressive pressure washers, metal brushes and strong chemicals. We'll get to why later.

General Cleaning Method for Composite Decks

Okay, so where do you begin with your regular maintenance? This is the case for most composite decking—it’s something you’ll need to do every few weeks (during the summer in Perth, less often in the winter).

First, sweep: Get rid of leaves, dirt and spiderwebs. Boring but necessary.
Hose it off: Get rid of surface dirt with a powerful spray setting. Nothing too aggressive.
Soap and scrub: Mix warm water with dish soap, then scrub sections in the direction of the grain.
Rinse well: Make sure to wash off all the dirt because it adheres to soap.

That's it for regular cleaning. Easy.

How to Clean Trex Decking: The Complete Method

Now let's talk about Trex specifically. As Trex PRO certified installers, there are some things we’ve picked up about how to maintain these decking projects.

If you are thinking about using Trex on your home, be sure to take a look at our full guide on Trex composite decking in Perth.

Trex has a protective coating that prevents staining and mould growth. However, that does not imply that Trex is unbeatable.

Regular Maintenance

Vacuum regularly to prevent staining from tannins in gum tree leaves.

Clean monthly with soap and water (dish soap is okay—don’t waste money on special cleaners).

Tougher Stains

Are you dealing with stubborn marks? Here's what works:

Organic stains: One part vinegar to one part water. Let it remain for 10–15 minutes, and then scour it.
Grease marks: A paste of baking soda (mixed with a little water) and scrub.
Mould spots: A solution of one part bleach to three parts water. Test it in an inconspicuous area first, as some of the colours on Trex can be finicky.

What NOT to Do with Trex

Never apply acetone, full-strength chlorine bleach or a deck “stripper”. These can erode the protective cap layer that makes Trex so strong.

The jury is also still very much in session for pressure washers. The company says it’s allowed to use one, but at less than 3100 psi and with the spray nozzle held at least 20 cm away from the deck surface.

Honestly though? It’s no more effective and pales in comparison to a garden hose with a little elbow grease.

Millboard Cleaning Guide: Keeping It Pristine

Millboard is a unique material, more plastic-like than wood fibre. The non-porous surface also means spills sit on top rather than penetrate, which makes cleaning easier but can be slick when wet.

Regular Care:

Sweep weekly (dirt doesn’t adhere the way it does on Trex).
Clean monthly with a thorough scrub using warm, soapy water and a stiff-bristled brush.
Pay special attention to textured grain details where dirt can hide.
Use a squeegee to remove any remaining water after rinsing.

Specific Stains:

Food, coffee, and red wine all react quickly with soapy water. They don't penetrate, which makes them simple.
Mould or algae: 50 ml bleach to a bucket of water. Use it, wait 10 minutes, scrub, and rinse. Millboard handles bleach well.
Oil and grease: Spray the deck with a spray-on deck degreaser purchased at the hardware store.

Millboard's Oddity

Hard water deposits or abrasive cleaners may cause a chalky appearance. Use a 50/50 mixture of water and vinegar to fix it. After mopping, give it a moment or so, and then rinse.

Common Mistakes That'll Wreck Your Composite Deck

This brings us to the surprisingly common mistakes you should avoid.

Mistake #1: The Wire Brush

Some people vouch for the effectiveness of a wire brush in eliminating particularly difficult stains. That person is wrong.

Wire brushes scratch the protective shell that seals in composite decking, leading to open pores and rough patches where dirt can collect readily. Use nylon-bristle brushes only.

Mistake #2: Letting Stuff Sit

That pot plant that died, the firewood you stacked and stored for ages, everything the kids left in one spot for a few weeks—they’re all choking on moisture underneath.

This is an ideal environment for mould and can also be discoloured. Move things around regularly.

Mistake 3: Using The Wrong Cleaners

Anything containing petroleum distillates, mineral spirits or harsh solvents is a no. Those “miracle” deck cleaners that supposedly breathe life back into wood?

Those are made for wood, not composite, and are more likely to damage than renew it.

Mistake #4: Ignoring the Gaps

The gaps between your deck boards are also worth the attention. Debris gets in, and moisture becomes trapped, which helps spur the growth of mould.

Scrape between your deck boards with a putty knife every few months.

Mistake #5: Overdoing it on Pressure Washing

We’ve already been through this, but let’s go ahead and revisit it. Excess pressure can ruin the texture on the surface of your composite decking by causing rough, fuzzy, or cloudy patches and possibly breaking down the fibres, which can void the manufacturer’s warranty.

Avoid using it, but if you have no choice, keep the pressure low and the nozzle constantly in motion.

Seasonal Maintenance Tips for Perth Conditions

Use these suggestions to modify your cleaning regimen because the weather in Perth can be extremely harsh.

Summer: Brush twice per week to get rid of the fine dust. Hose down quickly to prevent staining after barbeques. Examine the shaded corners for mould.
In the autumn: Don’t leave a leaf pile out too long, or tannin stains will follow. Organise and deep clean before the winter rains come.
Winter: Monthly mould checks are adequate. Our hot, humid environment is the perfect place for spores to proliferate.
Spring: Proper deep clean time. Tackle any stains now, ahead of summer entertaining.

Follow that seasonal rhythm, and your deck will be in tip-top shape all year without requiring heroic cleaning efforts.

When to Call in the Professionals

But DIY cleaning won’t always cut it, and that’s O.K.

If you have broad-ranging discolouration that just doesn’t seem to be coming off as well as you think it should, invest in professional plastic deck cleaning Perth services. We have access to commercial-grade cleaners that are composite-safe but have a greater impact than household products.

Observe any structural issues while cleaning? Professional eyes are needed to inspect for popped fasteners, loose boards, or movement in the deck structure. Little issues can grow rapidly in our climate, and addressing them early on can save money later.

On the other hand, if you’re getting major fading or discolouration in large areas, get an expert to weigh in. What appears to be stubborn dirt could actually be UV damage or a warranty-covered manufacturing defect.

We’ve seen our fair share of trex decks and Millboard decks in Perth here at Eco Carpentry, so we know what to look (and listen) for, and can fill you in.

Keep It Simple, Keep It Clean

When it comes to keeping a composite deck clean, you don’t have to make it a big job. Whether you’re rocking Trex decking or Millboard, it should just take a regular sweep and an occasional wash-down to keep things looking lovely.

The key is consistency. A little and often is better than leaving it for months at a stretch and then facing a mammoth cleaning project. Your deck is a lifestyle investment, and taking care of it can ensure you enjoy it for many years without any drama.

Do you have questions about your composite decking scenarios? Contact us at Eco Carpentry. We’ve built and maintained a fair few decks throughout Perth and, as such, have seen it all. We're always happy to help.

Now go out there and enjoy the thing – you deserve it after all that cleaning!

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How to clean your composite deck: step-by-step guide