Over the years, the quality and stability of the pressure-treated lumber for framing decks seems to have gotten progressively worse.
More than once, it is not uncommon to see adjacent 2x10s — that had been planed to a string line during construction — end up being nearly 1/2 inch out of plane six months later.
Not only is this sort of problem causing time-consuming reworks, it is disheartening to see a beautifully crafted deck deteriorate as the lumber shrank, warped, and twisted, creating uneven surfaces, lippage at joints, and sloppy-looking miters.
Advantages of Steel Framing
The name of the game with Steel Framing is precision. Every joist is cold-rolled (a galvanized steel sheet is pulled through a die that gives the joist its shape) perfectly straight and to the exact dimension you specify. No more crowning wet, heavy treated lumber, measuring joist depths, or planning after installation to flatten the deck framing.
Because the end joists are always straight, whether they are 8 feet long or 22 feet long, squaring a steel frame is child’s play. The rim (or band) joists are easy to install dead plumb, which makes installing the railing posts that much easier, too. All the corners will be exactly 90 degrees, 45 degrees, or whatever degree or radius you want them to be.
Even better, You not handcuffed by the span limitations of wood joists. Steel is able to span mind-blowing distances compared with wood. To stretch the span of wood joists, you might reduce the spacing from 16 inches on-center to 12 inches on-center, jump up to 2x12 framing, or double some members, but there’s only so much that wood allows you to do. On the other hand, to increase a span with Steel Framing, You can change the gauge of the steel, widen the flanges, or change the web depth to suit the design requirements of the project.
For instance, for a rectangular deck that’s 24 feet deep, 16 feet wide, and 11 inches off the ground, You would use 24-foot-long-by-8-inch-deep 16-gauge (54 mil) joists with a 2-inch-wide flange, and space them 16 inches on-center. The 8-inch joists would allow for air circulation below the deck. You would install a single flush beam 24 feet from the house bearing on two footings or helical piers. Designing that same deck with wood would require at least one, if not two, midspan flush beams, a plethora of joist hangers, and four times as many footings.
What to Watch Out For
Cost is a big hang-up for many customers. In most cases, steel framing material is going to cost more than wood. However, You end up using less material and fewer footings for a steel-framed deck than for a similar wood-framed deck, so depending on the design, the overall cost often ends up about even.
The labor cost to build a steel frame can be more or less than a wood frame, depending on several factors. For simple designs, steel is faster because there is no cutting whatsoever on the job site. Once the ledger is installed, the deck goes up like an Erector Set. The only tools needed are a cordless drill and an impact driver — no compressor, no air hoses, no saws.