Your composite decking needs a solid base. The base referred to here includes the foundation and the joists that the composite boards will be laid on. 

Also, depending on how high your decking is from the ground up, your decking might need a ground-level foundation. Or, an elevated foundation that raised the decking above the ground. 

For the ground-level foundation, the base will be installed on concrete slabs. If concrete slabs are not your choice, you can fix little posts in all corners of your decking.

Then you can attach the joists to the posts. If your composite decking is raised above the ground, you should fix long posts that will support the joists.

Note that your post depends on the height of your composite decking. You should make sure that the base is well cemented before attaching the joists to the posts.

How to build a solid base for your composite decking will be discussed next.

How to Build a Solid Base Composite Decking

Building a solid base starts with building the foundation of your decking.

Note that it was stated earlier that the foundation and the joists make up the base of your decking.

So, you have to be sure that you plan well when constructing your decking base. 

Step One – Determine the Location

You need to know where your composite decking will be situated before you start anything.

Is your decking close to the structure? Is there decking in your garden? Are you considering erecting the decking in an uneven landscape?

If you know where you want to install your decking, you will know if you are to use ground-level decking or elevated decking

Step Two – Build the Base 

A ground-level decking is perfect for a garden, while an elevated one is perfect for an uneven surface. Elevated composite decking is also perfect for double-storey structures.

The area where you will install your composite decking should be cleared. Grass and dirt must be scraped from the spot.

For ground-level decking, you should cover the spot with at least 50mm of gravel. 

preparing ground-level composite decking base

For elevated composite decking, dig holes where you will fix the pillars that will hold the decking. The pillars of your decking are wooden posts.

Then you should install the wooden posts to the ground with mortar. When it is strong, you can move forward to the following phase.

Step Three – Attach the Joists

Attaching the joists to the posts or concrete is the next thing to do. The joists that you should use must be made of high-quality materials like composite boards or pressure-treated wood.

Your composite decking will last a long time, so a composite board will complement it.

If you use untreated wood, the frame or joist will rot, and it will become a problem after utilising your decking for a long time.

The joist should run perpendicular to your house if you are installing it close to it. This is so that the composite boards should be installed parallel to your house.

If your composite decking is installed in a garden, then you should make sure that the joists and decking boards are perpendicular and parallel to one another. 

Make sure that the space between your joists is not more than 16 inches.

Step Four – Attach the Composite Decking Boards

You should start from the side of a wall or your building when installing your outdoor decking. The clips to use are starter clips.

Then, you should attach the other boards to the joists with T-clips. This fastening method is effective if you are installing grooved composite decking boards.

If you are using ungrooved composite decking boards, you can use screws. Be certain to leave at least 5 mm of space between the composite decking boards. 

The essence of doing that is to accommodate the expansion of the boards.

You can cover the rough edges of your composite decking with trims. The corner trims should be screwed directly into the joists. 

When your composite decking is done, you should tidy the surroundings and remove all leftover equipment. 


Your composite decking needs a very solid base for it to be fixed to the ground. You should follow best practices when erecting your decking.

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