How to Build a Steel Frame Deck

how to build a steel frame deck

When building a long-lasting composite deck, consider starting with a steel frame to help it last even longer.

After living a few years with a pressure-treated lumber deck, the boards have likely splintered or faded to a silvery gray that has a shabbier look than you’d like. If you’ve decided to replace the worn-out lumber with composite decking you have a decision to make. If there’s nothing wrong with your deck’s substructure you don’t have to tear it out, but if you’re going to the expense of replacing your deck boards with sturdy, long-lasting composite decking, you may wonder whether it’s a good idea to install it on a frame that will eventually rot.

Composite decking makes for virtually maintenance-free deck surface, but when it is built on a lumber substructure you may have to repair or replace your deck’s structure in just a few years. A steel frame deck with composite deck boards will last much longer, with only minimal maintenance and no major repairs. Many people don’t put in steel deck substructures because they don’t realize that steel is an option. It’s still new, and finding supplies and a knowledgeable builder can sometimes be a challenge. That’s why it’s helpful to have general knowledge about how to build a steel frame deck before getting started.

What Is Steel Framing?

When people think of steel framing they are probably picturing heavy steel I-beams, cranes, and a skilled worker stepping from beam to beam while carrying a bucket of rivets. But steel framing for decks is a light-gauge steel that is very similar to what is used for wall studs in commercial properties. It is a cold-formed steel made by passing steel sheets through a roller which folds the sheets into a U-shape.

These pieces come in dimensions that are approximately the same as lumber, but much stronger. Since we’re talking about steel, you might assume that it has to be welded into place. This isn’t the case. Light-gauge steel framing is installed with self-tapping screws, or screws that drill their own holes, in a manner similar to lumber. All these similarities to lumber make it easier to transition to building with light-gauge steel. Since steel is stronger than wood, you can substitute the equivalently designed pieces without worrying about whether your deck will support what you need it to.

The Advantages and Disadvantages of a Steel Framed Deck

The most obvious advantage of steel framing right off the bat is that it’s dimensionally stable. Unlike lumber, it doesn’t absorb moisture or dry out, and as a consequence it doesn’t twist or bow, which makes it a great complement to moisture-resistant decking. There are other advantages too:

  • It’s resistant to living threats. Wood is a large part of the diet (or home) of many creatures, from molds to termites to beavers. By not being on the meal plan of most of nature, steel framing can be enclosed without worries about pests moving in unseen.
  • It’s lighter and stronger than wood. Steel is a lot stronger than wood, which means that it takes far less weight in steel to support a deck than it does wood. This is an advantage in installation because it means that less effort is needed to set steel beams and joists in place while they’re being joined. This can speed things up considerably during building.
  • It has greater flexibility than wood. Due to being lighter and stronger than wood it is possible to span greater distances with steel beams and joists. Effectively, this makes it possible to build a larger deck with fewer posts. If you’re building a second story deck, this opens up more usable space below.

However, steel isn’t perfect and issues can arise. It is easier to damage steel framing than it is wood. The strength of this type of steel depends on the way it’s folded, and creasing it can destroy a piece’s strength. Since it isn’t available everywhere, replacing a damaged piece can take time, and put the entire project on hold. And while it doesn’t rot, steel can rust, and it depends on galvanization to resist corrosion. Whenever the coating is broken by cutting or drilling it will need sealing to prevent rust from gaining a hold. Still, steel has significant advantages over pressure-treated lumber, and when properly assembled it will outlast a wooden frame by a huge margin. When combined with high-quality composite decking boards, it makes for a deck that can survive almost anything.

How to Build a Steel Frame Deck

If you do decide on steel framing, there are some things to know before getting started. It’s important to note that you can order light-gauge steel framing at the exact length you need, which means there’s less to dispose of after the project. As a result of everything being cut to length, however, installation is a bit different than with a wooden deck:

  1. Installation of the frame begins starts with your steel beams. One of the advantages of using steel framing is that each piece of steel should be clearly marked.
  2. After unpacking the beams you will need to mark where the joists attach, and then install the brackets that will hold them in place with self-tapping screws.
  3. It is best to do this with the beams side by side to ensure the bracket spacing matches on both beams.
  4. Once these brackets are in place, the next step is placing the beam that goes to the house.
  5. Due to the steel being pre-cut, there isn’t extra length to work with, and you will have to precisely measure where your posts will go based on the beam attached to the house.
  6. Once this distance is determined, you can mark a line and place your posts either in concrete footings or in brackets that anchor them to footings.

Once the frame is in place, finishing the deck is largely the same as with a wood framed deck–you’ll screw your boards to the joists in the deck frame. Manufacturers of high-quality composite decking are aware of the many advantages of steel framing, and manufacture screws that are designed to screw into steel framing easily.

An example is the Hulk Fastener system made by Fortress Deck. This is a clip-and-screw fastener system that holds Infinity composite boards in place using a clip that inserts into a groove in the board. The steel screws have a Z-tip to drill their own hole in the steel, and a nano-coating to protect the screw and the steel from corrosion. In combination with a steel frame and Fortress’ fully-capped bamboo-based composite deck boards, they create a deck that can stay beautiful and last for years. These are examples of just a couple of the thoughtfully engineered offerings designed by Fortress Building Products that use unique technologies and processes to make high-quality, lasting products.

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