Do you need to seal composite decking? And if you do, how do you seal a composite deck? Good questions, and the answer depends on the brand and type of composite deck you have. Like clothing sizes, one size does not fit all. In other words, no two or three composite decks are the same.

Quality varies between brands, and even between products from the same brand. We can’t answer for all the different composite brands on the market, but we can answer your question, particularly as it applies to NewTechWood.

Composite Deck - Commercial Range - Antique

To Seal or Not To Seal?

Before we start, let’s state the obvious. Natural timber deck owners face a lifetime of regular deck maintenance – every 2 to 5 years they need to repair, sand and reseal to protect their deck and keep it looking good. That cheap deck they bought ten years ago has now substantially increased in “cost” for them and will continue to do so because maintaining a deck surface does not come cheap. Yes, you can do it yourself – is your back up to it? And you still have to buy the products required to maintain it.

Boards Sealed Around All Four Sides

Composite wood decking is manufactured from a combination of wood fibres and plastics, and when compared with natural wood decking, composite requires far less maintenance than the natural timber alternatives. For example, NewTechWood is manufactured from 60% recycled dense wood fibres and 35% high grade HDPE recycled plastics.

This core is then fully protected by a strong and durable polymer shield which covers every side of the board. Using a co-extrusion process this shield is heat pressed onto the core creating an impermeable protective barrier against moisture, ultra-violet (UV), insects and bacteria. We do all this to provide you with a durable deck that can be enjoyed over time without hard work from you!

In fact, with composite decking, the only “maintenance” required is to clean it occasionally – but you are doing this anyway regardless of what your deck is made from, be it timber, paving, or composite. UNLESS your particular deck is not sealed around all 4 sides. So, when buying a composite deck you need to ask the tough questions, one of which is: Is it sealed around ALL 4 sides?

Fully Capped Sides

Don’t Water Your Lawn While It Rains

If your composite is NOT sealed around all 4 sides, then it is exposed to weather and prone to insect infestation which can cause rotting and warping – the same as a natural timber deck. An unsealed timber or composite is not only vulnerable to those nasties, but also a victim of mould, fading and staining shortening your deck life as well as diminishing your deck’s appearance.

You are caught between a rock and a hard place if you have bought a cheap brand of composite decking to save money, only to discover you are up for ongoing maintenance costs just the same as if you had a natural timber deck. Rest easy, this does not apply to you if you are the owner of a NewTechWood deck.

Another consideration is if you do decide to use a sealant on your composite deck and it is already sealed, you may be voiding your warranty. Besides, deciding to seal an already sealed composite like NewTechWood is a bit like standing out in a rainstorm with an umbrella to water your lawn. Unnecessary and wasteful.

No manufacturers of quality, fully sealed composite decking recommend applying paints or sealants to their product.

If you are the owner of a first generation composite deck that is unsealed, or a more modern but cheaper version that is unsealed, we highly recommend you follow the advice of the relevant manufacturer regarding its upkeep. No two products are 100% identical in their make-up and what is suitable for one is not necessarily suitable for another.

But, in the spirit of THAT advice, do not apply a sealant to any NewTechWood product. We reiterate: all NewTechWood profiles, decking, cladding or screening, are already sealed around all 4 sides – protection that is backed by a 25 year Warranty.

When Do You Need To Seal NewTechWood Boards?

Note: The ONLY time we recommend using sealer on NewTechWood is to seal cut ends or edges that are going to be exposed to a lot of water, like around pools or spas. For small jobs of this nature, we recommend Crommelin’s Wet Look Paving Sealer. The rest of the board is already sealed and protected – leave it alone.

How Do You Seal Your Deck (if required)?

What we can tell you is before you seal any deck, you need to clean it thoroughly to remove any mould, stains, dirt and vegetation matter. If you don’t you will be “sealing” in any existing dirt you didn’t clear off. Don’t use cleaners containing harsh chemicals, e.g. chlorine bleach. These harsh chemicals can damage your boards. Likewise, the use of a power washer can also cause damage and should be used as a last resort under the manufacturers advise.

The safest method is to use a reliable deck cleaner suited to your deck type and a deck broom with soft bristles. If you are overwhelmed by cleaning product options, consider something like DeckWash. This is an Australian made product, made for Australian conditions and can be used to clean composite decking and natural timber. Too easy!


Once your unsealed composite deck is squeaky clean, you can commence the sealing process – using the sealant product your manufacturer recommends. Some suggest that water-based sealers are better than solvent based, because water based don’t change the colour of the composite deck and they can prevent mould growth.

Using a roller is recommended rather than a spray because a roller will help the deck more readily absorb the composite deck sealer, and thus the longer it will last.

Buy Fully Protected Boards

On the other hand, you shouldn’t use excess sealer because the composite can only absorb so much, and you will end up with sealant “pools” that have to be mopped up without smudging your efforts. If your back is not up to this type of physical work, you will need to hire someone to do it for you. Yes, more expense! You can see why buying a fully protected deck in the first place is a wise decision.

Sounding like fun yet? You didn’t sign up for this when you bought composite decking, did you? Let’s hope you didn’t buy one of those types then.

And if you are a NewTechWood owner, we know you didn’t. In fact, you probably aren’t even reading this blog… because it doesn’t apply to you.

Do You Need To Seal Your Composite Deck?

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