All outdoor decking needs a foundation for it to remain solid in the ground. Composite decking is not exempted because your decking foundation determines how long the decking will last. If you install or build your composite decking following best practices, it will last longer. But if you don’t build your decking foundation properly, your decking might collapse. So, what is the best foundation for composite decking? This write-up looks into different kinds of wood-plastic decking foundations and why you need them. 

Why Your Composite Decking Foundation Matters

Your decking foundation is the key to having a composite decking that will last long. When you build your decking, it will rest on its foundation. If the decking foundation is strong, it will sustain its weight and absorb any pressure placed on it when you walk on your decking. A weak decking foundation is no good for the decking and the decking owners. Composite decking, though a good flooring material, still requires a solid foundation to stay long. 

If your plastic wood decking foundation is not strong, you should not expect it to last long. There are various types of composite wood decking foundations. The foundation or footing you will give your plastic wood decking depends on the type of decking you want to build. If you build elevated composite wood decking, you will probably use posts or precast cement blocks as your decking foundation. But if you are building a flush or ground-level decking, you will use a cement block or sleeper system. 

Type of Wood-Plastic Decking Footing

We mentioned before that the type of decking foundation depends on the type of decking you desire to build. Let’s start with an elevated decking foundation.

Elevated Decking Foundation

An elevated composite decking is raised above the ground. This type of wood-plastic decking is some inches high and have space underneath. Homeowners usually build elevated decking in a garden that has an uneven landscape or to balance the level of the decking to the floor plan of the house. 

Using Decking Posts as the Footing

To build an elevated plastic wood decking, you have to use posts to raise it from the ground. The materials you use for the post of your decking depends on you. You can use treated lumber as the posts of your plastic wood decking. Or you can use metal as your wood-plastic decking posts. Treated lumber is the most common material homeowners using to build an elevated wood-plastic decking in their garden. Note that when using lumber, you should use treated lumber. 

This is because untreated lumber will rot and will not last as long as your composite wood decking. To construct the decking, you should clear the space and dig holes to put the posts. The height of the posts you will use as the foundation of your elevated decking depends on how long you want your decking to be. Put the posts after you have dug it, and then cover it with cement. Allow the posts to dry before you start building the remaining substructure of your decking. 

Flush or Ground-level Decking Footing

 This kind of decking footing is close to the ground. Unlike elevated decking raised some feet above the ground, flush decking provides a seamless walkthrough from your house to your garden. 

Using Cement Blocks as the Foundation

Cement or concrete blocks are good for a flush decking foundation. Using cement blocks does not require that you dig deep holes. You should clear the space you will build the decking and place the concrete block at different spots, ensuring that they hold your decking. Add cement to the base of the concrete block so that it will stick to the ground. 

Using Sleeper System as the Footing

decking foundation

Another way to build a foundation for ground-level decking is to use a sleeper system. A sleeper system is used to raise the decking slightly above the ground if you install the decking over a hard surface such as con concrete. Installing your decking directly on concrete might cause the joists to rot, but when you use a sleeper system to raise it above the ground, it gives your decking a breathable space and allow air to circulate under the decking.


What is the best foundation for composite decking? The best footing for composite wood decking is one that prevents the decking from collapsing. Depending on the kind of decking you are building, you can use posts, cement blocks or a sleeper system.

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