Composite decking is like other building structures, and it needs to be properly installed. You need a solid foundation for your composite decking. 

A strong decking foundation will make the structure safe to use for outdoor activities. Also, a composite decking that has a strong foundation will last longer. 

How you install your composite decking determines the kind of foundation you will give it. You can install your composite decking directly on the ground.

Also, you can build your composite decking above the ground. To build your composite decking on the ground, you need to install it directly on it.

For elevated decking, you have to utilize the post to raise it. Both methods of building composite decking need a foundation. 

Type of Outdoor Flooring Foundation

Composite decking can be installed directly on the ground or above the ground with posts. The two methods of installing composite decking will be discussed.

1 Ground Level Composite Decking Foundation

A ground-level composite decking foundation is very easy to build. First, you should know where to put your composite decking.

The essence is to create a level surface for your composite decking. You should remove all grass, rock, and dirty from the spot. 

Also, you should fill the spot with landscaping fabric which will prevent grass from growing under your decking.

 Gravel should be laid where you will install your composite decking. You should cover it with at least 50mm gravel. 

The gravel is useful because it will absorb moisture. Concrete slabs fixed at the four corners of your decking can be used instead of gravel. But make sure you don’t lay the joists directly on the ground.

If you will not utilise concrete slabs, you will have to dig holes at the four corners of your decking. Then you should fix small posts in the holes and cover them with cement.

The woods you will use as posts should not be as high as the ones you will use when building elevated decking. 

You will attach the joists of your decking to these posts.  The wooden posts replace the concrete slabs that were mentioned earlier. 

So, when building composite decking on the ground, you can either use concrete slabs or wooden posts.

The post and concrete serve as the foundation on which you will lay your joists.

How to lay your joists will be explained after discussing the elevated composite decking foundation.

from ground to up
raised decking project

2 Elevated Composite Decking Foundation

An elevated composite decking needs a very strong foundation. How high the composite decking is from the ground determines how strong the foundation should be.

The method of constructing elevated composite decking is similar to ground level decking. First, you have to clear the area where you will install your composite decking.

Ensure that the locale is free from grass or dirt. Then, you should dig holes at strategic spots where you will put the post. 

How many holes you will dig depends on how many posts you want to put and how strong you want the foundation to be. You should be sure to put posts in every corner of your decking.

Note that the height of the decking post depends on how high you want it to be from the ground. 

Since this is an elevated decking foundation, it should be high enough to raise the composite decking from the ground.

After digging the holes, you need to put the posts in them and cover the holes with concrete. Then the wooden posts will serve as the foundation of your decking.

So, you can see that composite decking needs a foundation. After building the foundation, you need to build the joists. 

3 Building the Joists

Your composite decking needs to be laid on the joists. The joists should be made of pressure-treated wood or composite boards. It is preferable to use composite boards. 

If you are tight on budget, you can use pressure-treated wood. But you should not use untreated wood to build your joists. Nails or fasteners should be used to fasten the joists to the posts.

Remember, the posts are the foundation of your decking. Attaching the joists to the posts will create a substructure that you will lay your composite decking on.

Then, you should lay your composite boards on the joists. The clips you will use are the T-clips and starter clips. If you are installing ungrooved boards, you should use screws.

seven joists used for decking project


Composite decking is like other building structures, and it needs a solid foundation for it to last longer.

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