How Wide Are Composite Deck Boards? (Profile & Size Guide)

If you are building a new deck in your yard, the first thing you need to do is measure up. Once you measure the space where your deck is going to go, you can work out how many composite deck boards you will need. Unfortunately, this isn’t always as easy as it sounds because the sizes can vary.

There are also multiple different profiles available, and knowing what the differences are and which profile is best for your particular project can be tough.

But don’t worry, this guide will tell you everything you need to know about the different composite deck board sizes and profiles so you can choose the right boards for your project.

How Wide are Composite Deck Boards?

The standard width for composite deck boards is 5.5 inches, but there are a few different profiles available. You can also find narrower and wider boards, but these are not as common. If you have a specific width in mind, be sure to check the profile before purchasing your boards.

If you check the specifications section on a manufacturer’s website or give them a call, they can give you more specific information about the sizes.

How Long are Composite Deck Boards?

Composite deck boards come in a variety of lengths, but the most common are 12 and 16 feet. If you have a longer or shorter space to cover, you can find boards that will fit, but they may not be as common. Certain brands like Trex, for example, offer composite boards that are 20 feet long.

The good news is, composite deck boards are easy to cut. So, you can cut the long ones to size for shorter spaces and if you need to put multiple boards together, you won’t have any seams.

How Thick are Composite Deck Boards?

How Thick are Composite Deck Boards

The thickness of composite deck boards can vary, but the most common size is 1 inch. This thickness is perfect for most applications, but if you have a specific need, there are options available that are thicker or thinner.

Thinner boards are better for projects where weight is a concern, like a deck that is going to be installed in an elevated position. Thicker boards are better for areas that will see a lot of traffic or high levels of moisture.

How Much Space Between Composite Deck Boards?

The space between composite deck boards is important because it affects the overall look and feel of your deck. If you have a lot of space between the boards, it can ruin the aesthetic. On the other hand, having a small gap is important for drainage.

The deck may expand in hot weather too and the gap allows for this expansion without putting excess pressure on the fixings that hold the boards in place. It’s also crucial that you make the spacing the same between all boards. You can use small plastic spacers to achieve this when installing the boards.

The standard spacing for composite deck boards is 1/4 inch – 3/16 inch, in most cases. You should not exceed a 1/2 inch gap between each board. If your deck runs against the wall of your home, you need to leave a 1/2 gap between the board and the wall. This gives it ample room to expand without coming into contact with the property.

Different Composite Deck Profiles

A deck board profile means the shape of the board. There are a few different ones to choose from, but the most popular are grooved and square-edged boards. Different profiles are useful for certain projects and each has its own benefits. So, understanding what profiles are available is important when planning a project.

Squared Edge (Solid Board)


This is the most traditional profile for a deck board. It has a squared-off edge and is completely solid. This type of board is best for projects where you want a more polished look or where the boards will be visible from all angles. You will usually use solid boards around the edges of your deck.

You will have visible screw heads when using solid boards, but you can get deck plugs to cover them. They are available in a range of colors that match your decking so the screws are barely visible.

Tongue and Groove Edge

Fortress Infinity is 1 in. x 5.35 in. x 8 ft. Oasis Palm Brown Composite Grooved Interlocking Deck and Patio Boards (2-Pack)

This is a more popular profile for deck boards. The tongue and groove edge allows two boards to fit together using hidden deck fasteners. This creates a stronger joint and makes the installation process easier. It also means you can get a completely smooth finish without any visible screws.

Solid Bottoms

Many composite deck boards have a solid bottom, meaning that they have a thick bottom and the same thickness throughout. The same shape that you would expect them to have. This makes for a stronger board, perfect for decking or any other application where it will need to take a lot of weight.

composite decking profiles scalloped, solid, and grooved

Scalloped/Grooved Bottoms

Some composite deck boards have a scalloped or grooved bottom. There are long grooves that run the length of the board, meaning that they have less overall material. These boards tend to be cheaper because they don’t use as much wood, and they are lighter too. However, you do sacrifice strength as a result. In most cases, they are still strong enough for decking, but it is something that you should take into consideration.

Hollow Board

hollow composite decking board ends

Hollow boards have a honeycombed center which is mainly hollow, aside from some supporting channels. The obvious advantage here is that they are very lightweight. They also respond less to temperature fluctuations, so if you are particularly concerned about them expanding in the heat, they’re a good choice.

On the other hand, water can sit inside the hollow boards, and even though you can cap the ends, it could still be a problem. They are also a lot weaker than solid boards.

Before starting a project, consider how important strength is, what your budget is, and how much moisture the boards will be subjected to. This will help you determine which profile is right for your project.

Related Questions

How Wide is a Trex Decking Board?

Trex decking boards are available in two widths; 3.5 inches and 5.5 inches.

Can You Cut Composite Decking with a Table Saw?

Yes, you can cut composite decking with a table saw. In fact, it’s the best tool for the job because you get quick, accurate cuts. However, you will need to use a blade designed for cutting plastic or composites. Standard saw blades can cause damage to the decking material. Make sure that the blades are sharp too.

Can You Bend Composite Decking for a “Curved” Design?

Yes, composite decking is the ideal material for a curved design. They need to be heated in a steam box beforehand, and then gently bent into shape before being installed. This can result in some amazing unique decking designs. You can find a great example in this article.

Final Thoughts

When choosing composite deck boards for your project, there are a few key things to keep in mind. The size is obviously a concern, but the profile is the most important thing to consider as this impacts the function and durability of the boards.

Solid boards are the standard and should be used for the edges of your deck, while grooved boards are ideal if you want a clean finish on the rest of the decking. Scalloped or hollow boards do have their advantages but make sure to account for the loss in strength if you use them.

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