If you asked 100 different people around our Atlanta metro area what the typical backyard deck is made of, it's safe to say 100 of them would say "wood" and exactly zero would say "steel".
Pressure treated wood is, by far, the go to material for deck builders to use for the structural frame of their decks. It's been around forever and is easy to get. Plus, it's wood, so it's something deck and porch builders are accustomed to working with. Pressure treated wood is like a comfy old sweatshirt for builders. You use it because that's what you've always used.
Just like anything, times change and technology advances. The newest trend with top tier deck builders like Peachtree Decks and Porches in the United States is using light gauge steel (like Trex Elevations) instead of pressure treated lumber for deck framing.
Steel is about as far away from pressure treated wood as you can get in the building materials spectrum but it has been used for a very long time in commercial construction. It's light. It's strong. It's durable. It doesn't warp. Compared to wood which is the exact opposite-heavy, weak relative to its weight, it can rot and it warps like crazy.
Think about your existing deck frame. You really don't see it unless you look for it. Standing on the deck you look down and see the deck floor and railings. Under the deck, if you have a patio, you are most likely looking out not up. Seeing the steel framing compared to wood is not really too big of deal for most people. And not for anything, I bet if you looked up at the wood joists under your current deck now it's not a pretty sight anyway with all the mildew, dirt and streaks up there. Of course, just like wood framed decks, steel framed decks can be made watertight with a ceiling if that's an option you're looking at.
The benefits of steel framing are real. Steel joists are stronger and can span longer than wood joists. What this means to you are less columns and beams under the deck. If your current deck has two beams and six posts, a comparable steel frame deck might have one beam and three posts. This is a great way to keep the area below your deck wide open and unobstructed. Also, steel framing is 100% percent dimensionally stable and true. It does not move, sag or warp over time--even in our intense Atlanta weather. Like composite decking and deck flooring, steel framing is manufactured to extremely tight tolerances and those tolerances translate to the fit and finish of the deck.
With a steel frame, everything is perfectly level, straight, square and plumb and it remains that way forever. The steel we use is galvanized to prevent corrosion and with certain systems like Trex Elevations, the framing members will also be factory painted.
Steel framing sounds expensive, right? Well, that can be a loaded question. Compared to pressure treated lumber sometimes it is more expensive and sometimes it's less expensive. With steel framing there is minimal waste as the framing comes cut to size to the job site. This saves time on the labor side. It's also lighter to move around and install which saves time. Factor in that on some deck designs, using steel uses a lot less footings and beams which saves labor and material.
On average, the cost difference for steel framing is 10 to 20% on the framing costs of your deck (not the entire deck because the decking, deck floor and railings are the same). Believe it or not, on some deck designs using steel framing can cost less than wood framing.
There is a real value in using steel framing and its something anyone building a deck these days should take a look at. Greg DiBernardo, of Peachtree Decks and Porches, has vast experience framing decks with light gauge steel and is the author of the "Framing Decks with Steel" in Professional Deck Builder Magazine which has become the manual for contractors across the country building with decks with steel. Just think...you have access to the guy that "wrote the book" for light gauge steel decking framing right here in Atlanta!