Which Composite Decking Can Be Installed Directly On the Ground?


There is ground level and then right on the ground deck. Are you thinking of installing composite decking directly on the ground?

A word of caution, despite composite decking designed not to require the same level of maintenance as wood decking.

Most composite decking should not be installed directly on the ground. The moisture and insects in the dirt will damage the decking. Composite decking needs ventilation to dry and separationfrom soil, to minimize the soil’s containment.

But there are some exceptions. Decking that can be installed close to or in the ground.

For obvious reasons the same decking that can be installed in contact with soil and can also be installed in high moisture areas. Therefore, decking that is safe for true ground-level decks can also be used for docks.

Before getting too far, let’s define a few terms.

What Is a Composite Decking?

Composite decking combines plastic (polyethylene) and a filler to add strength, increase performance, and reduce cost. The filler is often organic, commonly wood fibres, but some composite decking brands use rice hulls or bamboo fibres.

It is the filler that is going to make the difference for ground contact.

Pros and Composite Decking for Ground Contact Deck

It’s this combination that makes composite decking ideal for decking. Requires minimal maintenance, often limited to cleaning of the deckingOpens in a new tab..

Which is perfect. Being low to the ground will increase the amount of dirt and mud on the decking. Which can often stain wood decking but will have little impact on composite decking.

As long as you regularly clean the decking, it will look great. Or at least the top of the decking. But what lies under the decking is where the danger lurks.

How Ground (Dirt) Can Damage Composite Decking

It’s not the actual ground that can damage the composite decking but what is in the soil. Soil contains high levels of fungi and moisture, along with insects. Levels which most composite decking is not designed for. Composite decking is water resistant, not waterproof.Opens in a new tab.

And here is the crux. If the composite contains organic material, it can absorb water and rot. Or become infected by termites and the like as almost all infestation starts from contact with the soilOpens in a new tab. where most insects live.  

This is one reason why its so important to have the right ground cover under a deckOpens in a new tab.. To limit contact.

Organic material rots and is food for insects. Given the right opportunity, nature will have its way with it. Buried in the ground provides enough moisture and opportunity for insects to eat the organic material or for it to swell.

Either way, damaging the decking.

To be fair similar to pressure-treated wood. The plastic component of the decking will slow deterioration but if in contact will not as long as when installed correctly with ventilationOpens in a new tab.. Often 6″ (150mm) of the ground.

Composite Decking that Can be Installed in Contact with the Ground, Even Buried.

As I hinted before, decking without organic material can often be installed level with the ground or even buried.

First up is Deckorators Mineral-Based composite decking. Click the link for a full review about DeckoratorsOpens in a new tab.‘ unique composite decking. Ground contact is not the only thing that sets it apart.

“Voyage, Vault and Frontier decking as well as Porch Flooring are manufactured with Eovations technology, which allows these products to be installed in contact with the ground or submerged in water, all while covered under our warranty.”

DeckoratorsOpens in a new tab.

By removing the organic material, Deckorators can be on the ground and even in the ground. All without impacting their extended warranty.

WearDeckOpens in a new tab. has similarly replaced organic material. They use fibreglass instead. Making their composite decking ideal for ground contact and even for the harsh environment of saltwater docks.

“WearDeck is rated for ground contact and underwater installation.”

WearDeck

Another composite decking that is okay with installing in contact with dirt and water is MoistureShield.

“We offer the only wood composite deck board that can be installed in the ground, on the ground and underwater.”

MoistureShield

This is surprising as MoistureShieldOpens in a new tab. still contains organic fill wood fibres. But I guess their encapsulating process must be that effective in preventing the fibres from absorbing water.

Another company whose composite may be used close to the ground is TruNorthOpens in a new tab., I say may, because they do not advertently say so, but they use Rice Husk instead of wood fibres. The advantage of rice husks is lower water absorption, plus they do not harbour mould or fungi.

Not quite as good as Deckorators who entirely replace the organic material but still reduce the risk of ground contact.

Before you think that wood is the problem. I would not recommend installing FortressOpens in a new tab. or Calibamboo composite decking which is made with bamboo instead of wood. As bamboo being grass will readily absorb water. The straws that increase strength also pull water into the decking.

Tips for Building a Deck Level with the Ground

Regardless of which decking you use, all composite decking requires a strong substructure supporting the deck. You can use 2×4 for joists to reduce height for a smaller deck. Just make sure all wood in contact with dirt is treated for ground contact.Opens in a new tab. Often larger framing will provide better support for the decking.

Using landscape fabric on the ground before framing the decking will save you from endless irritation of weeds growing up through the decking. Choose fabric that allows water to pass through, preventing pooling and mosquitoesOpens in a new tab. but still preventing weed growth.

Building a Composite Over Concrete.

Another option is to build a low deck over concrete. Without the dirt underneath, most composite decking companies allow for and give instructions on building a deck over concrete. Which is an excellent option to refresh a worn patio without all the work and expense of removing the concrete.

“For sleeper systems where small debris (pine needles, leaves, sand, dirt) can accumulate either between or under deck boards, a minimum of 1-1/2″ (38mm) height is allowable.”

TrexOpens in a new tab.

Trex’s requirements of 1 ½” sleepers are almost universal.  

This Knucklehead isn’t installing composite decking but is of the more in-depth videos I have seen of installing sleepers over a concrete patio.

In most cases, a slightly raised deck is better for the decking and will make the deck more enjoyable. Elevating you out of the dirt.

But regardless, if you build a deck in contact with dirt or elevate it. Do consider some of these amazing composite brandsOpens in a new tab.. Or click the link to see what else is available.

Ryan Nickel

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

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