Steel Decking Substructures for Trex Decks

Historically, wood has been the go-to material for residential decking substructures. However, with the growing popularity of steel deck framing across the industry, more and more professionals are making the switch to recyclable steel for its superior structural integrity, design flexibility and eco-friendliness. In fact, it’s now possible to build a completely sustainable* and wood-free deck.


Steel substructures, like Trex Elevations® steel deck framing system, increase a deck’s longevity and value, while improving overall appearance both above and below. Unlike wood, steel won’t warp, twist, split or decay and its stability creates a remarkably flat deck surface. As the material is easy to cut and easy to build, it’s also more efficient and cost-effective for professionals to specify than pressure-treated lumber, resulting in less waste. Trex Elevations materials also are composed of 25 percent recycled steel, and any excess materials from a jobsite are 100 percent recyclable.

Offering superior durability and aesthetics, steel outperforms wood on a variety of levels:

  • Strength – Traditional wood framing can split, warp and shift over time, leading to an uneven surface in the deck boards above. Steel deck frames are precision engineered to ensure a refined, flat surface for the life of the deck. They also are significantly more resilient to weather, moisture, time and pest deterioration. Trex Elevations offers a 25-year limited warranty – surpassing pressure-treated lumber, which is chemically treated to resist decay for a maximum of 15 years.
  • Design flexibility – Have you ever tried to bend wood? Steel framing components have the ability to be bent and shaped to allow for everything from curves and angled corners to extended cantilevers. Additionally, they are more lightweight than wood and can span up to fifteen feet (vs. ten feet for wood), resulting in the need for fewer posts and greater flexibility in post placement. This creates less obstructed views and more open space below the deck for storage or even additional outdoor living area.
  • Sustainability – In addition to lasting longer than wood, steel deck frames are made from recycled materials, can be recycled themselves and, unlike pressure-treated lumber, are chemical free.
  • Safety – A substructure is the platform that will support your deck – not to mention your friends, family and loved ones – for decades of outdoor living activities. Steel offers superior strength and longevity, is non-combustible, termite-proof and free of pressure-treating chemicals.
  • With its ability to prolong the life of a deck and improve its overall appearance, steel deck framing delivers performance and design benefits that wood simply can’t. It’s a smart investment for any homeowner looking to maximize the life of their deck and a great product for contractors looking to deliver decks that will maintain their beauty and performance for years to come.

ABOUT THE AUTHOR. Mel Karlson is Senior Marketing Manager for Trex. For more information about Trex Elevations® Steel Deck Framing System, visit

Editor's Note: Virgin steel has a high embodied energy footprint. Although we like the idea of an ultra-durable deck structure, we feel that a 25% recycled content is not sufficient to counteract steel's high environmental impact. As this study points out, "The average embodied energy of virgin steel and recycled steel are 33.7 MJ/kg and 9.8 MJ/kg, respectively." Now that building scientists are starting to understand the long-term impacts of the INITIAL embodied energy of building materials (see article referencing this in our current issue), switching from PT wood to framing systems made with 75% virgin steel is would not necessarily be "sustainable" in the long run. Certainly, there's a case to be made for replacing pressure-treated lumber, which cannot be easily recycled due to its classification as a hazardous wase--with something. Recycled steel would be a good balance between environmental costs and performance/low maintenance gains. Trex decking, it should be noted, is an excellent product, with top-notch recycled credentials. But unless and until the company can find a steel source with high recycled content, we suggest you consider this new system a "work in progress."--Matt Power, Editor-in-Chief

Trex Reponse: Given that Trex’s decking collections are all made of at least 95 percent recycled materials, the recycled content of Elevations (at 25 percent) may not sound significant – however, we consider the combination of the two a remarkable achievement, and certainly an industry first. For cold-formed, light-gage steel framing, any higher recycled content would undermine the structural soundness of the system. While sustainability always is a priority at Trex, it is critical that we consider both environmental impact and safety when designing our products. We look forward to building upon the success of Trex Elevations while continuing to raise the bar on performance and sustainability – both for ourselves and the industry as a whole.