Rot Not, Want Not, Why Composite Decking Won’t Rot

The number one reason for replacing a deck is rot. The deck looked amazing when it was built. It may have even served your family for years, but now the decking is rotten. Making your deck a safety hazard.

What if you used composite decking this time? Would that prevent the decking from rotting? Does composite decking rot?

Composite decking is a combination of wood fibres and plastic, minimizing maintenance and rot. The newer generation of composite are capped with a polymer cap providing an extra layer of protection against decking rot.

Composite decking has many advantages and disadvantages, especially when compared to traditional wood decking. One of the biggest advantage of composite decking is rot. Or the lack thereof.

But before we get into the whys, let’s explain what we are dealing with.

What is Composite Decking?

Composite is a combination, or should I say composite of wood and plastic. The material is formed into decking boards often made to imitate wood planks for decks or porches.

What is Composite Wood Made of?

Composite decking’s main ingredients are wood fibres and plastic. Generally, a 50/50 blend, if you get really technical, often with capped composite 5% is pure polymer with the rest being an equal blend of wood and plastic.

The core of the decking is composed of recycled material. Waste wood fibres from lumber mills. The type of wood varies by decking brandOpens in a new tab.. Some limit the wood to oak sawdust or bamboo; others are not as discerning. 

Blended with post-consumer plastic composing of plastic bags, milk carton laundry detergent and the like.

There is always a percentage of ingredients not disclosed.  You know, the special blend of herbs and spices that make it unique.  But these chemicals do the hard work of making the plastic and wood hold together and last. In some like Azek, to decrease fire spread, others to minimize rot. Which is so critical for decking.

Why does Composite Decking Not Rot?

Opportunity, or the lack thereof. For rot to occur, you need 4 ingredients or elements.

  • Food
  • Air
  • Warmth
  • Water

Composite decking minimizes the food. The plastic is inedible.

The plastic content also reduces oxygen. As the decking core doesn’t readily absorb the air.

But the most significant reason is water. Composite decking has an extremely low water absorption rate.Opens in a new tab. So unlike wood that absorbs water (unless sealed), watering the fungi eating away at the decking. Water runs off composite decking, minimizing rot.

Some earlier generations of un-capped composites had mould and mildew grow on exposed wood fibres but now, with the polymer cap, even mould and mildew doesn’t grow on composite.

That recycled plastic is a real-life saver. At least for your deck.

How is Composite Wood Made?

Composite wood is an elaborate process of blending and co-extrusion in factories.

The wood fibres and plastic are blended together with heat and then extruded into usable wood planks.

I like to think of it like making sausages. Pre—cooked sausages where all the ingredients are cooked together and formed by pushing them through a form. The good ones include the cap in this process. Ensuring the cap and core are knitted tightly together.

Other Uses for Non-Rotting Composite Material

Other than decking, composite wood is commonly used for patio furniture, cabinets, sheathing, siding, that sort of thing. 

Many composite companies also offer composite deck railing. Allowing you to create the appearance of painted wood but without the maintenance, along with the non-rot properties of composite.

Trex has fully embraced outdoor furniture made from coOpens in a new tab.mposite material. We could write an entire article just about their furniture but in short, durable, low maintenance with a 20-year warranty.

Of course, Trex makes composite cabinets for your deck. Just learned that Weatherstrong does also. That I will need to research more sometime. The ever-expanding value of composite and deck improvements.

The biggest limitation for composite material is structural. Composite wood is known for its durability, but it has a different kind of durability. It was not made to be used for structural framing or other similar load-bearing destinies of such a calibre.

Composite Decking: Advantages Beyond Resistance to Rot

It Does Not Rot

Weather resistance is one of composite decking’s sexiest attributes. The artificiality and durability of the plastic existent in composite decking prove a force to be reckoned with against the weather’s attempts to eat away at your beloved family deck. 

Composite decking certainly takes the lead over natural wood decking when it comes to the sheer endurance of existence. Some even speculate that composite will take hundreds of years to decompose.

Since decks are enjoyed outdoors, mighty resistance against mother nature’s rounds proves to be a leading perk.

Over time, wood becomes susceptible to nature because it is nature. It can soak up moisture, permanently weaken, and rot away. Though there are measures you can take to avoid this from happening nearly as easily, that’s just it – all wood rots at one point or another, even if it takes a long time. With composite decking, you can avoid rotting altogether.


Remember a bit earlier when I shared what Composite decking is made of, wood and plastic. Recycled wood and plastic. Composite decking is almost entirely made out of recycled materialsOpens in a new tab., which is an immense help to the environment, the planet, and therefore ourselves.

Trex and MoistureShieldOpens in a new tab. use 95% content. FiberonOpens in a new tab. varies between lines but is between 94-96%. Making them all good choices for environmentally friendly decking.


Remember, there are different kinds of durability. IF you want structural or heavy load durability, Composite wood is not what you are looking for. However, if you are looking for an option that will truly stand the test of time in a physical sense, composite wood is your wood of the day. 

Composite decking is designed to weather well. To not be damaged by the sun’s UV. Resistant to years of rain falling on the deck.

Composite decking is made to last.

Less Maintenance 

Compared to natural wood, composite wood might as well have no need for maintenance at all. Since the stuff is renowned for its weather resistance, composite decking requires very few cleaning days, and those cleaning days are comprised of very few tasks.

“Fair Game” Quality

Unlike natural wood, the varying prices of composite wood and decking are not based on the durable quality of the composite itself, but rather on the various colours, styles, and textures. In short, composite pricing is purely based on the look and feel of it, rather than the durability. All Composite wood is durable.

Trex is a fine example of this. Trex Transcend, their best-looking solid composite decking has the same 25-years warrantyOpens in a new tab. as Basic Enhance their economical line. The same durable non-rotting composite is used in both.

The real difference is the cap’s appearance, not how resistant to rot the decking is.

Composite Decking: Disadvantages, The Price of Rot Resistance

Nothing is perfect, I’m afraid. Not even composite decking. Let’s be the devil’s advocate here and talk about why composite decking may not be for you.

Not Rotting is Expensive

Unless you are exotic wood for building your deck, composite decking will usually be considerably pricier than a natural wood decking job. The time, money, and resources it takes to make composite wood dwarfs the requirements for chopping up natural wood planks.

Composite prices will vary by brand and lineOpens in a new tab.. Generally expect to pay 4 to 6 times the price of 5/4 pressure treated decking. If you are looking for less costly but still durable decking Trex, Fiberon, TimberTech and UltraDeck all offer budget decking closer to 2 times the price of pressure-treatedOpens in a new tab..

Still more expensive but has less maintenance and greater durability.

Durable Against Deteriorate Makes Repair Impossible

One fantastic thing about real wood is that you can refinish it. There’s some roughness? Refinish it. Scratches that need to be buffed out? Refinish it. Needs a new paint job? Refurnish it. You can’t do that with composite wood. Why? Because you cannot refinish plastic.

If your composite deck becomes physically damaged in any way, there’s no refurnishing that unsightly gash on the composite deck. At that point, you’d need to buy a new board to replace your damaged goods.

For some composite like Azek, you can repair minor damages like furniture scratchesOpens in a new tab. with a heat gun. But it’s trickly and not perfect.

These are just a few of the pros and cons of composite deckingOpens in a new tab.. If you want to know more about the many advantages and disadvantages of composite, click the link. With every introduction of a new type of composite deckingOpens in a new tab., the benefits and drawbacks have evolved. Giving you one more reason to keep on top of what composite has to offer.

Ryan Nickel

A Red Seal carpenter, passionate about building decks to be enjoyed.

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