Selecting what materials to use is one of the most crucial parts of deck building. Much poor attention to choosing the right decking boards, but picking the best materials for the frame is also necessary. Without proper framing and joists, no matter how durable and high-quality your deck boards are, your deck can run into many problems. Not only can a poorly-designed frame shorten the lifespan of your decking, but it can also endanger people. The question is, what material should you choose for composite deck joists when flooring your backyard?

Choosing the Right Deck Joists

There are many options that you can choose from when selecting joists and frames for your deck. However, you will want to consult with your local building codes before considering your options. Not only are you legally required to follow them, but you can also ensure the structural integrity and safety of your deck, more so when you are building a standard deck attached to your house. 

With that said, you have freedom on what you choose to use for deck joists as long as it meets the bare minimum requirements stated in your local building codes. But with so many choices, which one is the best? It depends on your situation and preferences. Here are some of the best you can use. 

Pressure-Treated Pine and Other Woods

When it comes to framing, especially the joists, pressure-treated lumbers are among the most widely used. Pressure-treated wood is often from lower-quality and cheaper varieties of softwoods, and sometimes hardwoods as well. 

The process involves injecting the lumber with various chemical preservatives. The chemical treatment protects the wood from moisture, moulds, and insect problems, all of which are common wood decking issues. Because of this, pressure-treated lumber is an excellent choice for decking joists, which will be susceptible and exposed to the mentioned issues. 

While cheap, readily available, and weather and insect-proof, pressure-treated wood has its drawbacks. Unlike other options, it’s the least sustainable. The chemicals used to treat them are also often toxic. Sawing, installing and disposing of them require safety precautions. And lastly, they tend to crack and splinter more than other wood types. 

One thing to remember is to choose the right variety of pressure-treated lumber. Pressure-treated wood has various grades according to how much chemical treatment it received. For deck joists, higher quality will be better, or at least what your local codes will require. 

Cedar, Redwood, and Other Untreated Softwoods

deck joists for backyard

If you don’t like using chemically-treated wood, there are a few more options that you can select. One of which is using untreated softwoods. Despite what many people might think, a few varieties of softwoods are among the best choices for decking. Some can even be as good as some hardwoods. They are also highly resistant to insects, moulding, and rotting. 

Untreated softwoods are safe, sustainable, and good-looking. You won’t regret using them as deck joists, or even as decking boards. With that said, untreated softwoods are slightly more expensive than treated wood. Compared to pressure-treated, they are less weather-resistant and require more maintenance. However, they are less prone to cracking and splitting issues. 

Some of the most popular softwoods are Western Red Cedar and European Redwood. Not only are they commonly used for decking boards, but they make excellent wood joists as well. They are naturally resistant to pests and moisture. They can last more than a decade. 

Composite Lumber

Since decking joists will face many issues, you’ll want something durable and weatherproof. While pressure-treated wood and untreated softwoods make excellent decking frames, they are still wood. Over time, you will have to encounter issues such as warping and rotting. 

As an alternative to wood, many use non-wood framing and joists to prevent problems. One of the best options is composite lumber. If you are building a composite deck, it’s worth considering choosing composite joists as well. They are waterproof and durable. 

While composite lumber can be slightly more expensive than most wood, many agree that the added price is worth it. Unlike pressure-treated wood, they are not toxic to animals and humans. They also require less maintenance than that of softwoods. They are also resistant to insect damage. 

Metal Joists and Frames

Aside from wood, metal is also a suitable material for frame and joists. While uncommon, they are among the densest, most durable, and longest-lasting materials. They don’t have the same issues with using wood. And in terms of structural integrity, almost nothing can match them. Some examples of metal materials used for decking and framing are stainless steel and aluminium.

However, the downside of using metal is its high cost. It’s also harder to transport and install, not being DIY-friendly. For this reason, many rarely used metal decks in residential settings.

Which One Should You Choose?

Overall, pressure-treated is the best material if you are on a budget. They are cheap, weather-resistant, and durable. If you don’t mind spending a little, untreated softwoods are safer and more sustainable options. But if you value quality, you can consider using composite lumber due to its waterproofing, long-lasting, and low-maintenance properties.