6 Composite Decking Installation Mistakes to Avoid


The extreme climates now experienced in many parts of the country demand that anything built outside must be made from rugged materials able to withstand sub-freezing temperatures, heavy snow, wind-driven moisture, and extended periods of high heat and humidity. That’s why most professional builders agree that building a deck with high-quality composite decking materials is the ideal choice.

However, even the best composite decking product in the world won’t perform as well as it should if it’s not installed correctly. Here are five mistakes to avoiding when installing – or hiring someone to build – a new composite deck at your home.

1) Weak Deck Framing

The #1 reason that decks fail prematurely is not from too much weight, per say, but rather from the deck’s ledger board being incorrectly fastened to the frame of the house. In addition to selecting the right type of hardware to make the actual attachment, the ledger board must also be flashed correctly to allow any water to drain down and out from under the finished wall assembly. As with any lumber, minimizing exposure to moisture is key to maintaining a solid, strong bond with the home.

2) No Lag Head Screws

A tell-tale sign of a potential problem with the ledger board attachment is the absence of lag screw heads.  If the only fasteners you see are simple nails or screws attaching the ledger to the house, it’s worth having a professional take a closer look before proceeding with the installation of new composite decking. The fix could be as simple as adding the appropriate number of heavy-duty lags to the existing frame. 

3) Joists are Set Too Far Apart 

Another mistake to avoid when installing composite decking is spacing the joists too far apart. Current building codes require that all decks should be supported with a minimum of 2”x 10” pressure treated pine joists that are spaced 24” apart (although 16” OC is standard building practice). So, keep in mind that some additional framing may be necessary if you decide to upgrade your existing pressure treated wood (PT) deck with a high-quality composite material. Any small investment in additional framing material will be well worth the increased stability you’ll experience for the lifetime of the deck.

The good news for homeowners is that unlike most composites, DuraLife® hardwood composite decking products can be installed between 20” O.C. (on-center) at 90° to 16” O.C. at 45°.

4) Deck Footings Not Deep Enough

Another common mistake that should be avoided is improper installation of concrete footings. Extreme freeze/thaw conditions can wreak havoc on concrete footers if they are not installed below the frost line. Here in Maine, that can be 48” or more. Again, a little extra effort here can go a long way to making your composite deck feel sturdy and secure for years.

Installing concrete footings at the correct depth allows the footing to absorb the expansion and contraction of the material surrounding it as it freezes and thaws without causing the footing itself to shift – taking the deck with it. 

5) Incorrect Fascia Installation

The most common mistake we see with fascia installation is the practice of extending the fascia to cover the ends of the decking boards. This improper installation method allows dirt & moisture to be trapped in the gap between the fascia and decking and often causes the fascia to eventually warp or pull away from the outer rim joist.

Deck boards (including perimeter boards used for picture-framing) should be installed so they extend past the outer rim joists by less than 2” lengthwise and 1” width wise. The ½” thick DuraLife fascia boards should then be installed below the decking boards and fastened to the outer rim joists using #8 x 2” stainless steel capped composite deck screws or #9 x 1-7/8” fascia screws (similar to the Starborn Deckfast Fascia System). 

When fastening, always leave a 1/8” gap between the top of the fascia and the bottom of the deck boards. Use three fasteners, equally spaced across the width of the fascia board at the top, middle and bottom locations of the board (2 fasteners for riser boards) and spaced approximately every 12” along the length of the board. Never place fasteners closer than 5/8” from the edge or ends of the board and make sure to leave a 1/8" gap at butt joints and adjacent to fixed objects. 

6) Using Screws to Secure Deck Boards

Attaching decking to the support framing boards below with screws has been the method of choice for deck builders for many years. While the advancements in screw technology have improved their ability to be installed without stripping, screws can still be difficult to work with – especially with composite deck installations. Settling for a screwed down composite deck is yet another common mistake to avoid.

Even when the screws are installed perfectly – they can clutter up the otherwise clean and smooth look of a beautiful composite deck panel that’s been engineered to mimic the look and feel of Golden Teak, Brazilian Cherry, Tropical Walnut wood. It’s just not a great look.

The Cleaner Alternative: Hidden Fastener Systems

Instead of using screws, composite decking makers have designed hidden fastening systems that create a clean, smooth surface while providing a solid, stable connection to the deck frame. Rather than installing screws through the top of every deck board, clips are first attached to the framing boards and the decking is then attached to the clips.

DuraLife Step-Clip™ composite decking hidden fastening system can reduce installation times by up to 50 percent.  Other benefits of the DuraLife Step-Clip system include providing complete joist protection (no tape needed) and is designed to automatically create a uniformed 3/16” space between each composite deck board.

Raw Materials and Manufacturing Processes Matter

The biggest mistake that consumers can make is investing in a ‘legacy’ composite material that hasn’t been improved upon since the 1990s.  DuraLife composite decking products are uniquely manufactured with a super-strong, co-extruded polypropylene outer shell that forms a “force field” around three sides of the board. This makes DuraLife exceptionally resistant to staining and fading compared to older generations of composite decking from other manufacturers.

DuraLife’s ColorLock™ Multi-Layered Finishing System also helps protect against discoloration because composite material is completely uniform from one side of the board to the other. Made with a proprietary mixture of polypropylene plastic and hardwood fibers, DuraLife composite decking is inherently more resistant to damage from moisture buildup, mold and mildew growth.

Get samples of DuraLife composite decking and have them shipped directly to your door. Choose your samples now!  

This article is made possible by DuraLife. DuraLife’s unique polypropylene and hardwood composite decking materials simply outperform all other wood and composite decking products. More solid and safe under foot, DuraLife decking is backed by a 25-year warranty. It is stain and fade resistant, mold and mildew resistant, and is available in the colors and deck railing options you want. Get Samples, try our Composite Deck Visualizer, or contact DuraLife now to learn more.