Composite Decking: Installation Tips

Installing composite decking sometimes requires the use of special fasteners and fastening techniques designed specifically for synthetic products. Composite decking is fabricated from a combination of polymers (plastics) possessing properties that will produce a durable, resilient building material that is virtually maintenance-free. Composite decking is manufactured to resemble the texture and the appearance of natural wood, but will last almost indefinitely and is much more expensive than ordinary lumber.

It is available in a variety of colors that imitate the natural tones of common wood species. There are many manufacturers and distributors of composite decking systems offering products that often come with a unique set of specifications and installation instructions. This article will discuss some of the basic techniques used for working with composite materials in general.

The Basic Components of a Composite Deck

Decking (either composite or wood) is available in nominal dimensions of 5/4 x 6 inches. The decking will be fastened to and supported by the framework consisting of vertical posts and horizontal joists installed perpendicular to the decking. It is typically only the decking that is made of composite materials; the structural frame is constructed with pressure treated lumber. However, all of the deck components – decking, posts, joists, railing and balusters – are available in composite materials. 

Working with Composite Materials

You can cut composite decking just as you would ordinary lumber – with a circular saw. The sharp edges on the end cuts can be beveled with a belt sander. Cut each board square and have the joints positioned at the center of the joist. Use a jigsaw to cut out notches where a post or a downspout penetrates the decking. Unless you are using fasteners specified by the manufacturer, composite decking is generally fastened to the frame with deck screws that require pre-drilling. A pre-drilled hole is drilled with a diameter slightly smaller than that of the screw. Make sure that the screw heads are set at a depth either flush with or slightly below the surface of the decking. This can be accomplished either by using a countersink, or simply by using a smooth-face hammer to drive the screw home.

Some Additional Helpful Tips

Before installing the composite decking, make sure that the wood framework is stable and structurally sound. Replace any members that are damaged or rotting. Whether you work in toward the house or start at the house and work outward, make sure that the outer-most edge board is installed parallel with the deck frame. Cut and layout several rows of decking at a time before fastening the boards to the joists. Composite decking, like wood, is often bowed or crowned. Check that each board is being installed straight as you secure it to the joists. Like most materials, composite decking will undergo thermal expansion. Allow for this by leaving a 1/8 inch gap between boards. A couple of #12 nails left in the gap will insure uniform spacings as the boards are fastened to the joists.