If you’re DIYing your deck build, it’s important to understand deck board spacing requirements for your chosen deck material. Deck board spacing refers to the gap between the sides of the deck boards and between the ends of the deck boards.
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.
Expansion & Contraction of Common Deck Materials
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 understand the importance of deck board spacing, you’re ready to dive into the recommendations for TimberTech® decking in comparison to traditional lumber.
Side-To-Side Deck Board Spacing
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 1/8” 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.
It’s typically a good idea to let your wood boards sit out in a dry area for one to two weeks before installing them to allow for proper acclimation.
Side-to-Side Spacing With 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 Side-to-Side Spacing With TimberTech Decking
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.
TimberTech Capped Polymer Decking
TimberTech AZEK® capped polymer decking spacing requirement:
A minimum of 1/8” to 1/4” side-to-side gap 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 1/8” to a maximum of 3/16” side-to-side gap, depending on which fastener you 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)
The board shoulder type has to do with how the sides of the board look. There are two shoulder options:
- Square shoulder
- Grooved (pictured)
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. Fasteners can be either top-down fasteners or hidden clip fasteners, and certain fasteners are only compatible with certain board profiles and shoulder types.
Curated Deck Board & Fastener Pairings
If you’re uncertain about which deck boards and fasteners go together, we’ve got a cheat-sheet for you. Check out these curated pairings for a winning combination.
TimberTech AZEK With Cortex® Hidden Fasteners
Cortex top-down fasteners are hidden with plugs made of TimberTech deck boards for a refined, seamless deck surface.
TimberTech AZEK With TOPLoc® Color-Matched Screws
TOPLoc top-down fasteners are color-matched screws that blend into your deck surface for a polished look.
TimberTech PRO & EDGE With CONCEALoc® Hidden Fasteners
CONCEALoc hidden fasteners are installed between grooved boards, giving you a fastener-free surface.
End-to-End Deck Board Spacing
End-to-end deck board spacing refers to the spacing — if any — between two ends of a board that meet, called a butt joint.
Traditional wood decking is often installed with no gap between the ends of the boards because wood primarily expands along its width, so there is little risk of buckling at butt joints.
As you’ll recall, TimberTech decking expands and contracts along its length, so proper end-to-end spacing is critical. The end-to-end deck board spacing recommendations depend on which TimberTech product line you choose.
End-to-End Spacing Recommendations by Decking Lines
For TimberTech Capped Polymer Decking
TimberTech AZEK decking does not require an end-to-end spacing gap, just like traditional wood. This is because of its unique material makeup, which won’t buckle due to expansion with a tight install.*
For TimberTech Capped Composite Decking
TimberTech PRO® and TimberTech EDGE® do have specific end-to-end spacing requirements.
The spacing you’ll need to account for will depend on the outdoor temperature at the time of installation.
*Be sure to keep TimberTech AZEK decking as cool as possible during installation to avoid changes in length.
Water Drainage & Airflow
Besides accommodating expansion and contraction of the boards, deck board spacing also helps with water drainage and airflow — which is especially important for traditional wood decks.
Drainage & Airflow Concerns for Wood Decks
For a traditional wood deck, insufficient gapping can increase the chance of moisture damage to the deck surface and substructure, which can cause issues like:
- Mildew, mold, and/or rot
- Cracking, splitting, or warping
- Frequent deck board replacement
Drainage & Airflow Concerns for Composite Decks
For a TimberTech composite deck, there’s little concern of moisture damage to the surface of the deck. However, insufficient gapping can cause moisture build-up on the traditional wood substructure, which could cause issues to your deck’s structural integrity. Maintain at least a 1 ½” space below the deck boards to allow for airflow.
Get More DIY Guidance
Now that you have a firm understanding of deck board spacing, you’re ready to explore more resources to complete a successful DIY build you can be proud of.
Explore the Deck Building Resource Center for more installation insight with easy-to-follow videos, step-by-step installation guides, and more helpful DIY considerations to guide you.