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Deck Board Spacing by Material: What to Know

Deck Board Spacing by Material: What to Know

Deck board spacing refers to the gap between the sides of the deck boards and between the ends of the deck boards. If you’re DIYing your build, it’s important to understand the optimal spacing between deck boards for your chosen deck material.   

How Much Space Between Deck Boards? 

Side-to-side spacing: Typically 3 mm – 6 mm, depending on deck material and fastener type

End-to-end spacing: Depends on decking material 

Deck board spacing between deck boards with l-shaped couch and end table on composite deck

Why Proper Deck Board Spacing Is Important 

✓ It allows enough space for the deck boards to expand/contract without buckling. 

✓ It provides space for water drainage and airflow

✓ Helps avoid moisture build-up which can cause mould and mildew.  

Expansion & Contraction of Common Deck Materials

Recommendations for spacing between deck boards are not universal — they vary between decking materials due to how different materials expand and contract.  

Board expansion and contraction affect deck board spacing between deck boards

Expansion & Contraction by Material 

The most common types of decking material expand and contract in different directions: 

✓ Traditional wood expands along its width

✓ Capped polymer and capped composite decking expands along its length. 

Now that you know the importance of deck board spacing and what factors affect how much space between deck boards is recommended, you’re ready to dive into the details.  

Get the insight you need on everything you need, from types of composite decking to budgeting your project.

Side-To-Side Deck Board Spacing

Side-to-side deck board spacing between deck boards recommendations

Side-to-side spacing refers to the gap between the length of the boards.

Side-to-Side Spacing With Traditional Wood

Traditional wood decking is typically installed with a 3 mm gap, as long as you install the boards after they have dried out and acclimated to your local climate. If installing freshly treated wood, install it tight (no gap) to allow for the shrinkage. 

To acclimate your wood boards, let them sit in a dry area for one to two weeks before installing them.  

Always refer to the installation guidelines for your chosen deck material before breaking ground on your project. VIEW INSTALL GUIDES 

Side-to-Side Spacing for TimberTech Decking 

TimberTech capped polymer and capped composite decking will not shrink side-to-side at all after installation, so it’s essential to get the correct spacing right at the time of install. 

Factors That Affect TimberTech Decking Side-to-Side Spacing 

The decking line and board profile and shoulder type you choose will influence which fastener options you’ll be able to use. 

Side-to-Side Spacing Recommendations by TimberTech Decking Line

The decking line and board profile and shoulder type you choose will influence which fastener options you’ll be able to use.

Deck board spacing between deck boards with Board profile and shoulder type affect which fasteners you can use

What Is Board Profile & Shoulder Type?

The board profile has to do with how the underside of the board looks. There are two board profile options: 

✓ Full profile (pictured) 

✓ Scalloped 

The board shoulder type has to do with how the sides of the board look. There are two shoulder options:   

✓ Square shoulder 

✓ Grooved (also pictured) 

Side-to-Side Spacing Recommendations by TimberTech Decking Line 

TimberTech Capped Polymer Decking

TimberTech AZEK® capped polymer decking spacing requirement:

A minimum of 3 mm – 6 mm side-to-side spacing between the boards, depending on which fastener you use. 

TimberTech Capped Composite Decking

TimberTech PRO® and TimberTech EDGE® capped composite decking spacing requirement: 

A minimum of 3 mm to a maximum of 6 mm  side-to-side spacing, depending on which fastener you use. 

No-Stress Spacing

Use our deck spacer tool for an even easier deck installation.


Side-to-Side Spacing Recommendations by Fastener Type

Once you’ve chosen your decking line and board type, you’re ready to choose your fastener type which will help inform how much space between deck boards you’ll need. Fasteners can be either top-down fasteners or hidden clip fasteners, and certain fasteners are only compatible with certain decking linesboard profiles, and shoulder types

The side-to-side deck board spacing gap you go with is essential in calculating how much decking you’ll need for your build. LEARN MORE

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