Deck Board Thickness 101: What to Know & How to Choose

October 6, 2020

You might think all deck boards are alike — but in reality, there are important distinctions to think about. For example, deck board thickness can vary across our composite decking portfolio, and across different kinds of traditional wood decking. Need to know how to pick the right deck board thickness for your project? And which options are available to you? Keep reading — and don’t worry, we won’t lay it on thick.

Deck Board Thickness: Why It Matters

To begin, it’s important to note the difference between standard deck board thickness and the heftier alternative.

Deck Board Thickness: Standard = 1” thick. Thicker deck boards, such as TimberTech® AZEK® MAX boards, are 1.5” thick.

There are three major reasons why the thickness of your deck boards will matter. Those are:

  • Material strength: Weaker wood will need to be cut thicker to support the structure.
  • How far apart your deck joist spacing will be.
  • Type of build: Deck board thickness can vary depending on whether you build a residential or commercial structure (like a dock).

Let’s break down each one.

Deck Board Thickness by Material Strength

When it comes to traditional decking, the species (or type) of wood you build with impacts the overall performance and longevity of your deck. Why? Because different types of wood are stronger — or weaker — than others. Certain tropical hardwoods, for example, are hardier than common pressure-treated woods like cedar or pine.

Your strongest decking material option won’t be wood at all, but capped polymer deck boards.

TimberTech AZEK Decking MAX Deck Board

MAX Deck Boards

These thicker boards are the strongest option for minimal movement. They can span the widest joist spacing (more on this below) and are often used for boardwalks or docks.

The Takeaway: Greater deck board thickness impacts the build and performance of your deck.

Deck Board Thickness by Joist Spacing

The primary reason to choose thicker deck boards over standard? If you need more than the conventional 16” spacing between the center of your deck joists.

Thicker deck boards allow for more space between your deck joists.

Deck Board Thickness Spacing for Deck Joists

What Are Deck Joists?

Deck joists are the heart of your deck’s substructure. They support your deck boards, which fasten onto the joists from above. The greater the space between the joists, the stronger your deck boards need to be — and wood can’t compete with the strength of capped polymer decking.

What Is "On Center" for Deck Joist Spacing?

Your deck surface is made up of deck boards fastened to your joists at regular intervals, measured from the center of a given joist to the center of the adjacent joist. That measurement is called “on center.”

  • 16” on center = standard for residential applications.
  • 24” on center = required for some commercial applications and commonly used for docks and boardwalks; made possible by increased deck board thickness.
Joist Spacing for MAX Deck Boards

The Takeaway: More joists = more labor = higher overall labor and substructure cost. The greater you can space your deck joists (because of thicker deck boards), the more you save upfront.

Deck Board Thickness: Residential vs. Commercial

Harvest Collection by TimberTech AZEK in Slate Gray with Island Oak MAX deck board thickness

There will be different building codes and requirements depending on whether your build is residential (like a composite deck in your backyard) or commercial (like a dock, boardwalk, or similarly high-traffic area).

Maximum joist spacing for standard TimberTech composite deck boards is 16″ on center for residential applications. TimberTech AZEK MAX boards can span 24″ on center, making them ideal for docks and boardwalks.

Distressed Traditional Wood

Traditional wood dock showing signs of mildew and damage.

Get the MAX Benefit

Unlike traditional wood, TimberTech AZEK MAX boards:

  • Boast the thickness for minimal movement and serious durability.
  • Provide a sturdy underfoot feel.
  • Stay incredibly resistant to moisture and protect against mold, mildew, and rot thanks to their innovative capped polymer construction.

As always, when installing any decking products, you should closely review the appropriate decking installation guides and local building codes. Working with a TimberTech-registered contractor is recommended.

The Takeaway: Greater deck board thickness means a sturdy feel underfoot, minimal board movement, and the heft to perform in coastal conditions.

What Are My MAX Deck Board Options from TimberTech?

Slate Gray Harvest Collection TimberTech AZEK

TimberTech® AZEK® Harvest Collection®

Slate Gray

Coastline Vintage Collection TimberTech AZEK

TimberTech® AZEK® Vintage Collection®


The best way to evaluate board thickness is to order samples of both standard and MAX decking so you can see and feel the difference for yourself.

See & Feel the TimberTech Advantage

Our capped polymer and capped composite decking lines combine recycled material with all the beauty of traditional wood.

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