How to Install Extruded Composite Decking

Installing composite decking instead of traditional wood decking is an easy way to nearly eliminate traditional maintenance requirements. While some composite decking options are almost identical to lumber in their shape and workability, extruded composite decking has gained popularity because it is both lighter and less expensive than other composites. Installing extruded composite decking is more difficult than installing a typical deck, but still a doable project for many homeowners.

This project assumes that you are installing composite decking on an existing deck. To begin, you should remove all of the old decking and any old fasteners that might damage your new deck. Then you should check the underlying structure for any potential damage or structural members that should be replaced. Then, with the underlying structure sound and complete you can begin installing the new composite decking.

Extruded composite decking requires a starter strip that covers the end of the first piece, concealing the fact it is not a solid board. It is a narrow piece of composite that contains the groove for the tongue and groove boards. Install this piece by screwing into the board and into the structure of the deck below with galvanized screws. Space the screws according to the manufacturer’s instructions: 8 inches is typical for the starter strip.

Slide the first piece of composite decking into the grove and screw at an angle on the exposed “tongue” into the structure below. You want to make sure that there is a screw at every junction where a structural member meets a board that crosses it. Keep in mind that extruded composite decking can be fragile until it is installed; for longer pieces get a helper to hold the other end and help place the lumber. You should also plan on leaving a gap that is at least 3/16″ between boards or whatever the manufacturer’s recommendation is.

Some pieces will abut handrails and other obstacles. For these pieces, carefully mark the where the post or obstacle is placed in relation to the board and cut away that section. You can work with composite decking just like typical lumber, so almost any saw would be suitable for the job.

Another thing to keep in mind when installing composite decking is to stagger any vertical joints. This is better both structurally and visually for your deck. Most manufacturers recommend a one third/two third installation. This means you begin by installing a full sized board and then install a two third size board. The next board should be only one third the size of a full board. By beginning the installation this way you are assured that the joints are staggered.

When you reach the other end of your deck you will need to install a support block to stabilize the groove end of the last board. Each manufacturer has different requirements for the support block, so follow their instructions carefully for the placement and size for your particular composite material.

Installing extruded composite decking requires one additional step to make it look its best. While you can leave the ends of the composite exposed, most homeowners cover the ends of the deck with a piece of composite fascia. These are easily installed by screwing from the back of the fascia and into the back of the composite board. Keep in mind that the fascia is installed so it is flush with the top of the deck.

Extruded composite decking is an easy to use product but that does not mean that every homeowner is well equipped to complete the installation process. If you have no woodworking experience, consider contacting a professional who can do the job for you.

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