A Guide to Installing Composite Decking From Fiberon and Trex

Composite decking is a great way to refresh an aging deck or build a new one that will last for decades. As a leading building materials supplier in the Midwest, Spahn & Rose partners with two composite decking suppliers—Fiberon and Trex—to help you design and build your next great outdoor project.

While the basics of deck construction are essentially the same whether you’re using wood or composite, there are a few differences that are important to remember as you install composite decking.

Note: This document covers the basics of deck and joist orientation, installing fascia, positioning deck boards, and attaching them using screws or hidden fasteners. While this guide is meant to give you a general idea of the process, you should always refer to the Trexor Fiberonwebsites for complete instructions.

Storage of Composite Decking

If you won’t begin installing your deck right away, composite decking should be kept flat, supported and covered to prevent sagging, warping and other damage. Because it is also prone to expansion in warm weather, your decking should be kept out of direct sunlight as much as possible to keep your cuts and board positioning as accurate as possible.

Deck and Joist Orientation

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Proper ventilation is critical to the longevity of your deck. Air needs to be able to flow underneath the deck to keep the area relatively dry and the additional space allows for proper drainage. Fiberon recommends a minimum of 1½ inches between the ground and the bottom of the joists to allow for ventilation and drainage.

Joist positioning is the other important factor to consider when setting up your deck’s foundation. Trex requires that all decking boards be supported by at least three joists, and both Trex and Fiberon have maximum allowable joist spacing for various board orientations (such as perpendicular, diagonal or specialty patterns like picture frames or tiles).

Special consideration needs to be paid to the joists if you plan for them to bear heavy loads such as a hot tub or large planters. Trex recommends that you consult a professional engineer about code-appropriate joist spans for heavy loads. If you’re especially concerned about the appearance of joists under your decking board, the tops can be painted black to help conceal them.

Installing Fascia

Fascia is a non-structural siding used to conceal framing material and give your deck a consistent look from all angles. Fascia should be installed before decking to make sure the boards are installed with the proper overhang for a clean appearance. Fascia need to be installed with the same gaps and specialty fasteners to allow for ventilation and prevent cracking. The sections below discuss the specifics of gaps and fasteners.

Setting Your Composite Decking Board

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Once your frame and joists are built, it’s time to start laying out your decking. Because many of Trex and Fiberon’s products are made to mimic the natural color variations of wood decking, they recommend that you lay out your complete deck before fastening anything in place. This will help identify places where color variations are too similar or visually jarring.

To increase the visual appeal of the deck, consider alternating the direction of the wood grain from one length to the next. For Fiberon boards, the wood grain pattern repeats every 44 inches. Stagger the arrangement of your decking to achieve the desired visual effect.

When arranging your decking, be sure to leave the required gaps end-to-end and between boards, as well as between the outside deck board and any permanent structures. These gaps are critical to allow for drainage as well as expansion as outdoor temperatures rise. Both Trex and Fiberon have recommended gap widths based on the outdoor temperature at the time of installation:

  • For Fiberon decking, recommended end-to-end gaps range from 1/32 inch to 1/4 inch depending on the temperature during installation. For side gaps, the recommendation is 3/16 inch, with 1/4 inch between the outside board and a permanent structure.
  • For Trex decking, the recommended end-to-end and side gaps range from 1/8 inch to 3/16 inch, depending on the temperature during installation. The gap against the permanent structure ranges from 1/4 inch to 1/2 inch, depending on the installation temperature.

If your deck is built with metal framing and joists, they will expand differently than wood. As a result, minimum gapping for your deck board will be different as well. Refer to your chosen product’s installation guide for specific details.

Once you have your whole deck laid out and are happy with the patterns, it’s time to start fastening your composite decking board in place.

Fastening Deck Board

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One big selling feature of composite decking is its clean look when installation is complete. Both Trex and Fiberon accomplish this in two different ways, so it’s important to fully read the instructions and make sure you have the appropriate fasteners before beginning.

Trex Hideaway Universal Hidden Fasteners are the recommended fastener for all Trex products. Additionally, there are a variety of composite-specific decking screws available on the market. These are specifically designed not to crack or shred the composite material as they are installed. Trex composite decking is grooved along the sides to conceal the fasteners.

Fiberon recommends the use of Phantom clips and fasteners and Cortex hidden fasteners. These composite-specific screws need to be installed in pre-drilled holes and are then capped with plugs to conceal the holes. Cortex plugs are designed to color match most of Fiberon’s composite colors, allowing for a clean finish over your whole deck.

For both products, the ends of each board need to be screwed twice into a joist, and end-to-end junctions should be fastened to two joists for extra security. Both Trex and Fiberon have minimum lengths from which screws can be fastened to the end of boards. This is to prevent cracking, both during installation and as a result of future expansion and contraction.

Once your deck is assembled, it’s time to move on to installing additional features like posts and railings. For more information, assistance with measurements and on-site delivery, visit Spahn & Rose and speakto one of our representatives.