Strongest Decking, Does Wood or Composite Decking Fail? (3 tests to compare)


A good strong deck, built with decking that will not crack underfoot, be marred by a chair’s foot or pebble. And be left sagging between joists. Simply put, decking strong enough to be enjoyed for years. With many decking options available, which is the strongest. Are you better to install wood decking for strength or composite?

Wood decking is many times stronger than composite decking. When comparing how much pressure is required to break or deform the decking. Wood decking is sturdier than most composite decking on the market. Withstanding multiple times the level of stress that will damage composite.

There are three methods of testing decking strength. It helps to compare each with simple numbers, not subjective testing like “feels solid.” Tests, that allow you to know the strength of the decking long before you load it, into your truck. Knowing the strength of the decking.

The three matrixes to compare decking, either wood or composite, are

  • Modulus of Elasticity [MOE]
  • Modulus of Rupture [MOR]
  • Hardness

Don’t worry, these are “scientific terms,” but I will talk of them as a carpenter, which I am. Just a neighbor talking over the fence about the strongest decking. Explaining terms and what they mean to you building a deck. Not only numbers in a lab but explanations for your deck.

Before getting too far into the weeds. Most composite deckingOpens in a new tab. and the popular wood 5/4 decking, all are roughly 1″ (25mm) thick. Designed for to span 16″ (400mm). Regardless of which decking you choose, wood or composite, the deck substructure will have a more significant role in determining how much weight the deck can holdOpens in a new tab. than the decking. But the stronger the decking is, the less blocking supportOpens in a new tab. it will need and the less potential for damage.

When comparing decking wood vs composite, we need to be specific about wood types. Not all wood is created equal, nor is wood decking. There are significant differences between Ipe, an extremely tough hardwood decking and pine. Pine the most common tree used for pressure-treated decking. Which most decks are built out of.

Another common decking wood is cedarOpens in a new tab.. More specifically, Western Red Cedar. It is a beautiful wood that can be stained, preserving its originally wood grain beauty or allowed to grey but preserved by its natural preservatives.

When it comes to wood decking, cedar is the weakest of the three standard options. Treated pine decking is in the middle of the pack for strength but very budget-friendly. Ipe is in a league of its own, with few deckings, wood or synthetic being as strong as Ipe. It is hard to beat and even harder to break.

The number of offerings of composite decking is even greater and expanding. But overall, as a group, composite decking is not as strong as wood decking. Their strength varies by formula and manufacturers. We will compare four popular composite brands, which will give an idea of composite decking strength, with three wood options. But as you will see, even between composite decking boards, there are differences in strength. One number does not represent all.

I can safely say that treated wood decking is more robust than composite, but it depends on which composite board by how much.

Which Snaps Easier, Composite or Wood Decking?

Modulus of Rupture [MOR], or simply bending strength, is one way to compare decking strength. When I say bending here, I am not saying deflection. That feeling under your feet as you step unto the decking. Softening your steps, as the decking bows between the joists. Deflection often dictates joists spacing and how firm the deck feels but does not tell how breakable the decking is.

Modulus of Rupture [MOR], is how much pressure is required to crack or break the board. The decking “rupturing” under pressure. Like blowing a tire on your truck. How much weight can the decking support before coming apart? The force required to put your foot through the decking.

Before getting into the detail, it amazes me how much weight is required. I have snapped decking with a hard boot. I never thought I was exerting that much pressure. But this is continues building pressure, not a karate chop, bringing the crowd to their feet.

 MOR PSI
IpeOpens in a new tab.25 660
Treated PineOpens in a new tab.12 800
CedarOpens in a new tab.7 500
TrexOpens in a new tab.4 351
Fortress ApexOpens in a new tab.3 771
Deckorators (WPC)Opens in a new tab.3 327
TimberTechOpens in a new tab.3 157
Decking Modulus of Elasticity [MOE]

The chart is in ascending order. With TimberTech composite deckingOpens in a new tab. breaking the easiest, and Ipe wood being the strongest. Another thing to note, the three strongest deckings are all wood, the composite are all below. Being the weakest decking for breaking, by bending.  

There is no significant difference among the composite decking, but Trex is the least likely to snap for composite deckingOpens in a new tab. when bent. Requiring almost 40% more force. A substantial difference between composite decking but insignificant when compared to wood.

The one up from Trex is Cedar, a softwood decking. Is twice as strong as most composite decking. You could tie a TimberTech and TrexOpens in a new tab. board together, and cedar would still take more to break.

I don’t’ know if I need to continue, but composite decking is three times more likely to snap than pine decking. A great budget option and considerably stronger in a snapping competition.

Ipe decking is a league of its own. Durable pine decking is not even half as strong as Ipe for snapping. So, when comparing Ipe to composite decking, there is no real comparison. Ipe is the strongest.

Ipe is the outlier, but all-wood decking is more robust under a bend test than composite.

This is one reason why you are so limited on how far composite decking can overhangOpens in a new tab.. The greater the overhang, the more pressure and bending will occur. Composite decking, with its low bending strength, is more limited when overhanging.

Modulus of Elasticity [MOE], What Does It Take to Deform the Decking?

Elasticity, as opposed to Rupture, is the difference between blowing through and bending to deform. Rupturing is when the fibres of the decking tear apart from the stress. When they don’t return back after pressure being applied, they are deformed.

A stretched elastic band vs blown tire.

Decking with a high elasticity will spring back after deflecting under your feet. Again, the question is not how much the decking bends but what it takes for the decking not to bounce back after.

Or think putty in your hand. How hard do you have to squeeze the decking before changing its shape?

“modulus of elasticity [MOE] quantity that measures an object or substance’s resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it.”

Wikipedia

A little different from a crushing test or hardness test, which we will get to.

Crushing test is about destroying the cohesion of the material, elasticity about the shape of the material.

Hardness is the ability to penetrate into the decking, but we will discuss that more later.

Which takes more pressure to deform, wood or composite decking?

 MOE PSI
IpeOpens in a new tab.3 200 000
Treated PineOpens in a new tab.1 790 000
CedarOpens in a new tab.1 110 000
Deckorators (WPC)Opens in a new tab.548 742
TimberTechOpens in a new tab.542 200
TrexOpens in a new tab.432 213
Fortress ApexOpens in a new tab.237 861
Decking modulus of elasticity [MOE]

Again, wood decking is in a category to itself. With all composite decking taking less pressure to deform. Wood taking two, three or six times more force to distort than the strongest composite decking. 

Again, Ipe is one of the most indestructible decking options. Modulus of Elasticity [MOE] is about maintaining the decking’s shape. And Ipe takes and an incredible amount of pressure to distort it. If fact 3 200 000 psi, that’s like elephants standing on your decking and if it was Ipe, not doing anything. Composite decking would be a pancake under those elephant’s feet.

Fortress apex is the easiest to deform on the chart. This may be because of its PVC core. Deckorators (MPC) has with a PVC core have similar low results. PVC decking may be cooler than compositeOpens in a new tab. but much more pliable, in a bad way.

From the same company, Deckorators (WPC) scores much better. Almost twice the strength of Apex but at the same time, half the strength of Cedar.

Take the strongest composite decking on this list, and its only a third of the strength of pine decking to deformity. There is just no getting around the fact that plastic bends. And when it bends, it doesn’t always bounce back. There is a reason we make bows out of willow trees, not plastic pipes. Wood bounces back better than composite. 

Last, when comparing wood or composite decking strength.

Comparing the Hardness of Composite Decking Vs Wood

Another thing to consider in decking strength is how hard it is. When your big fat uncle, can we say that? Sits down in the deck chair. Will the chair leg leave a mark? How much weight can the decking support before becoming indented forever? Or will a small rock stuck in the sole of your shoes leave marks wherever you step on the deck?

The answer to these questions and what will prevent marking on the decking is the decking’s hardness. The harder the decking is, the less marking will happen on your deck.

Testing decking hardiness is called the Janka Hardness Test. Using a  0.444″ (11.28mm) ball, yes, the size is very precious. Pushing the ball halfway into the material and measure how much pressure is required. This gives us our hardness decking number. And how hard you need to step with a pebble to damage the decking.

 Hardness lbs
IpeOpens in a new tab.3,510  
TrexOpens in a new tab.854
Treated PineOpens in a new tab.690
CedarOpens in a new tab.350
TimberTechOpens in a new tab.225
Decking Hardness

Sorry, we lost two of our comparison decking, lack of reliable data. But these five still tell the story reasonably well.

Again, Ipe decking is off the charts. It is a tough material. Few decking, if any, is as strong as Ipe decking. On the flip side, this actually makes a very hard decking to work with. Requiring pre-drilling for screws and machining is a task in itself. Cutting with a saw will quickly dull your blades. Amazing wood requiring an amazing and patient installer.

The surprise on the hardness scale is Trex composite deckingOpens in a new tab.. Trex decking is less likely to become indented than all the other wood decking. The capping on this decking is the true hero. Providing a high level of protection plus the decking’s actual core is denser than other decking. Preventing ugly indent marks from showing up on your deck.

But before saying the composite deck is harder than wood and less likely to mark. TimberTech comes in at the bottom. Even less than cedar deckingOpens in a new tab., which always has been a softer decking. You have to work so carefully on it as not to mark it.

Treated pine deckingOpens in a new tab. again holds the middle ground. Not super hard but not easily indented. Overall, just a good decking.

Conclusion of Which is Stronger, Wood or Composite Decking?

If the strength of the decking is most important to you, wood is the way to go. Yes, wood decking has more maintenance, but it is a stronger decking than composite.

One possible exception is the hardness of the decking. Trex’s cap is very durable, supported by its composite core, which has its advantages. Once the decking is all supported by blocking and installed, its stiffness and potential for deformity are reduced.

Making Trex decking a viable option even when scoring lower in the other two categories.

For more comparison between wood and composite decking, click hereOpens in a new tab..

Ryan Nickel

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

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