Determining how long a deck will last often determines if building a deck is worth it. Or how much money to spend on a deck. If the deck will only last a few years, you will only spend a minimal amount on it, but if it lasts decades, your budget can increase considerably. As you will get many more years of enjoyment out of it.
There are a number of factors that determine how long a ground level deck will last. Which we will discuss, but the short answer is.
On average, a ground-level deck will last 15 years or more. A ground level deck’s life is vastly dependent, not on the decking but the environment under the decking. With the deck so close to the ground, the deck’s substructure is at risk of failure, shortening how long the deck will last.
Of course, this is an average. I have replaced decks less than 15 years old and enjoyed ground-level decks that are over 30. How long a ground level deck last is greatly determined by design and construction.
Before discussing how to extend a ground-level decks life, let’s define a ground-level deck.
A ground-level deck does not have to be level with the ground.
In short, a ground-level deck is any deck that is close enough to the ground as not to require safety railing.
In the United States, this is 30″ (762mm) in Canada, a ground-level deck is any deck less than 24″ (600mm) above your yard.
Because of its proximity to the ground, even at 24″ (600mm) high, a ground-level deck will not last as long as a raised deck. As the closer to the ground, the deck is the faster it will deuterate and rot.
Just like a tree. A dead tree will stand in the forest for years without decaying. But once it falls on the ground, it will quickly rot and disintegrate.
The same is true with a deck. Ground-level decks being closer to the ground will rot sooner than a raised deck.
But there are a few things you can do to extend a ground level deck’s life.
Starting first with the decking.
Decking that will Last Longer on a Ground Level Deck.
The decking is the most noticeable and is the number one reason why someone will replace their deck. Regardless of use, once the decking starts to rot or break, the deck is no longer of value.
For a ground-level deck, you want decking that can be exposed to higher levels of moisture. As being so close to the ground, they will dry less and have more humidity trapped below.
Pressure-treated decking is a good start, as it is treated to prevent fungi growth, extending the decking’s life. Untreated decking will quickly rot outside close to the ground.
“Minimum ground clearance required 50mm over concrete, 150mm over dirt. Drainage and airflow beneath the deck is also very important to ensure a good looking long term deck.”Trex
Most decking must be installed 6″ (150mm) or more above grade. Any closer is considered ground contact and will fail. A notable exceptions are Moisture Shield decking, which is rated for ground contact. Its propriety design prevents failure even with ground contact, by preventing moisture from being absorbed by the wood fibres.
TimberTech also is a good option for lasting ground level decking as it is wrapped on all four sides of the decking. Preventing moisture from penetrating into the decking.
This can happen with Trex decking and similar composites that have an open side on the decking underside. As they are wrapped only on the top and edges, leaving the bottom of the decking exposed to the moisture trapped under the deck.
Upgrading to a PVC or non-organic decking like Decorators, which has mineral-based instead of organic like wood fibres. Ever seen a rotten rock? Me neither the same idea with mineral-based decking close to the ground.
But regardless of how good of decking you install on a ground level deck. The deck’s substructure will ultimately determine how long the deck last.
The decking may last fifty years like Azek decking, but the deck is finished if the joists collapse.
For starters, select the right joist material.
Most decking is installed on treated lumber, but not all lumber is treated for ground contact.
Ground Level Deck Will Last Longer with Joists Treated for Ground Contact
Since the deck is built low to the ground, make sure your joists are treated for the extra fungi in the dirt.
In deck construction, material 6″ (150mm) or less from the ground is considered in contact with the ground. Incised lumber treated for ground contact may not look as nice as appearance grade lumber, but it will last longer under your deck.
If your deck is within 6″ (150mm) from the ground, using wood treated and stamped “for ground contact” will make it last longer.
Speaking of treatment. You may be able to get away with it with a raised deck far removed from the ground, but all lumber used for as ground level deck should be end treated after every cut to prevent fungi from rotting out the core of the wood.
When you cut the board, it’s apparent the treatment does not penetrate the entire board when you can see the untreated wood in the centre. Which is now exposed to fungi if not treated. End treatment seals of the ends like a completing the blanket of protection around the wood, protecting the wood from fungi.
One thing that treated wood is not treated for is moisture. Water trapped under or in a deck will rot out the boards regardless of how much treatment. The water rotting the joist, not the fungi.
Under Deck Venting will Help a Ground Level Deck Last Longer
One reason a raised deck can last longer than ground level deck is ventilation. A deck with three or more feet of drying air underneath the deck allows the wood to dry after rain preventing rot.
A ground-level deck does not have this but doesn’t mean it doesn’t need to dry out or can’t.
A ground-level deck needs to be built with ventilation in mind.
There are a few ways to help a ground level deck dry out.
The first is with the decking. Larger gapping on the deck will help moisture to escape from under the deck.
It may not seem like much, but on a 12′ square deck, increasing the decking gaps from 3/16″ to ¼” will increase ventilation by almost two square feet, with over 30% more room for air to circulate. But when you think of air’s actual physics, a 30% larger gap will circulate even more air than the additional space.
Another way to help ground level deck ventilation is with the skirting. A ground-level deck should have an open underside to allow air to blow under the deck, drying out the ground and joists.
If having an open underside deck is undesirable either because of appearance or critters under the deck. Design the deck with lattice skirting or gaps between the skirting boards to allow moisture to escape from under the deck.
Eliminating Standing Water Under a Ground Level Deck will Help It Last Longer
Similar to ventilation, the treatment of the ground under a ground level deck will impact its longevity.
Decks need to drain, and so does the water under the deck.
Putting a layer of gravel under the deck will aid in drainage. Helping the water to dissipate away from the deck. Helping the joist and decking to dry after rain.
Using landscape fabric under the gravel will increase drainage while preventing weeds from growing up through the stones.
A wet climate that receives a lot of rain sloping the ground under the deck to encourage water to run out will also help reduce damage caused by excess moisture under the deck.
Regular Cleaning of a Ground Level Deck Will Make It Last Longer
This may not seem essential to extend a deck’s life, but it is the simplest way to. Ground-level decks being closer to the ground will collect leaves from trees and mud from the yard. Which traps moisture on the deck, shortening its life span.
Especially in the little gaps between deck boards. These narrow gaps collect dirt and leaves that act as a sponge trapping water on the decking’s joist and edge. Slowly over time, rotting the decking and the top of the joists.
To prevent this, regularly wash the deck and clean out all the gunk between boards with a pressure washer or scrub brush. It may not seem important, but it will extend the deck’s life, years.
Also, during construction, you can use joist flashing. This helps protect the joists with an extra layer of protection, preventing water from getting into the wood. Both by shielding the exposed gaps between the decking while sealing around the screws preventing water from penetrating into the joists.
It’s the little things that make all the difference, but if you do the little things a ground level deck will last decades. Giving you an outdoor space to enjoy for years.
Conclusion of How Long a Ground Level Deck Will Last
A ground level will rot quicker than a raised deck, but it doesn’t haven’t to. If you use joist treated for ground contact, seal the ends. Install them above a gravel base, allowing water to drain away, along with ventilate the underside.. A ground-level deck can last for decades.