HomeOutdoor Living BlogSolid vs Grooved Composite Decking: Differences & Fasteners

Solid vs Grooved Composite Decking: Differences & Fasteners

December 2, 2021
Grooved composite decking installation for grooved composite deck boards

While the image in your mind of a standard deck board is likely that of a smooth-edged rectangular board, composite decking comes in a few different profiles. In addition to the solid-edge board you’re familiar with — called a “square-shoulder” board — you also have the choice of grooved boards. Grooved composite decking is one type of deck board that features grooves along both sides of the board, ideal for hidden clip fastening systems.

So why is it important to think about different composite deck board shapes?

✓ Because the type of deck board you choose will affect your installation and final deck appearance, as different fasteners are designed to work with specific deck board shapes.

Discover your decking options and get the insight you need on choosing the right boards for your project. READ OUR DECKING SERIES

Follow these steps to determine whether square-shoulder (solid edge) or grooved composite deck boards are right for your project.

Step 1: Learn About Composite Deck Board Shoulder Types

Board shoulder type refers to how the sides of the board look.

TimberTech® capped polymer and capped composite deck boards feature two board shoulder types:

Board Shoulder Types

grooved board


A board with capped grooves along both sides to allow for hidden fastening.

square shoulder


A solid-edge board that allows for easy top-down installation. Square-shoulder is sometimes referred to as a “solid” board.

How Do You Groove Composite Decking?

Easy — you don’t. All TimberTech decking lines and collections feature a grooved board option, so you don’t have to groove your own boards.

TimberTech grooved composite deck boards feature capping in grooves

TimberTech Grooved Composite Decking

Our encapsulated grooved boards feature protective capping that runs through the grooves for maximum protection.

If you find yourself in a situation where you need to groove a TimberTech square-shoulder board, you can add a groove. Be sure to follow the installation guidelines for your chosen deck boards.

Now that you know your composite deck board shoulder options and that TimberTech offers superior grooved composite decking, you can next ask:

  • What are my fastener options?
  • Which fasteners are compatible with each board shoulder type?
  • Which board type and fastener pairing gives me the installation and final appearance I’m looking for?

Step 2: Discover Your Composite Decking Fastener Options

The type of deck board and the TimberTech decking line you choose affect which fasteners you can use.

Why? Because certain fasteners are designed specifically for grooved composite deck boards while others are designed for square-shoulder boards.  

Grooved composite decking installation with hidden clip fasteners

Hidden Clip Fasteners

Fasteners that are installed along the sides of boards, giving you a clean, fastener-free surface. 

Grooved composite decking top-down fastener installation

Top-Down Fasteners

Fasteners installed through the deck board face into the joist below. You can also achieve a clean, fastener-free surface with top-down fasteners

Familiar With Top-Down Fastening?

Then upgrade your wood deck to TimberTech, which shares many of the same installation best practices as traditional lumber.

Step 3a: Discover Hidden Clip Fasteners for Grooved Composite Deck Boards

Thinking about grooved composite deck boards for your build? Explore these compatible hidden clip fasteners to decide which is best for your project.

Installation of grooved composite decking with CONCEALoc hidden fasteners


COMPATIBLE WITH: All TimberTech grooved composite decking.*

Simple, one-step installation.

Faster install time thanks to pneumatic installation with collated screws (installation can also be hand-driven: pictured).

Installation of grooved composite decking with FUSIONLoc hidden fasteners


COMPATIBLE WITH: All TimberTech grooved composite decking.

Superior hold strength thanks to three points of contact between the board and joist.

Faster install time thanks to pneumatic installation with collated clips and screws.

TimberTech EDGELoc Deck Fasteners Installation Step 3


COMPATIBLE WITH: Only TimberTech EDGE® grooved composite decking.  

✓ Easy-to-use with a consistent 7/32” gap. 

✓ Faster installation thanks to 12-clip collated strips and pre-set screws.  

*Refers to TimberTech capped polymer and capped composite decking lines.

Interested in top-down fasteners for grooved boards?

While certain top-down fasteners can be used with grooved composite deck boards, remember that the main reason to choose grooved boards is for their compatibility with hidden clip fasteners.

However, you may use a combination of top-down fasteners and hidden clip fasteners for your project. For instance, top-down fasteners will need to be used to secure the boards closest to your home.

Step 3b: Discover Top-Down Fasteners for Square-Shoulder Composite Deck Boards

Square-shoulder boards are compatible with both visible and hidden top-down fasteners to suit your preferences and project needs. Note: For TimberTech AZEK square-shoulder boards, we recommend top-down fasteners.

Discover Your Top-Down Fastening Options

Choose from either visible or hidden top-down fasteners.

Top-down fastener installation for grooved composite deck boards

Step 4: Consider Grooved vs Solid Composite Decking

Now it’s time to take what you’ve learned and determine whether grooved or square-shoulder (solid-edge) composite decking is right for your project.

Deciding which deck board shoulder type is best for your project will depend on how you value these factors:

  • Installation ease
  • Final deck appearance

Installation Ease: Grooved vs Square-Shoulder

Each board type and fastener pairing requires different installation methods, but easy, straightforward options are available for both board shoulder types. You’ll also need to make sure you have access to the appropriate tools for your chosen fastening method — either by buying them or renting them.

Installation of grooved composite decking with CONCEALoc hidden fasteners


Grooved composite decking installation is fast and easy with collated clips and compatibility with pneumatic tools.

Get the details of installing grooved TimberTech PRO® decking with CONCEALoc hidden fasteners.

Top-down fastener installation with grooved composite deck boards


Square shoulder boards are ideal for easy top-down installation, which is the common method used for installing traditional wood decking.

Find out more about top-down installation with Cortex® screws for TimberTech AZEK decking.


See Grooved Composite Decking Installation

Get a feel for grooved composite decking installation by watching an install video using CONCEALoc hidden clip fasteners.

Final Deck Appearance: Grooved vs Square-Shoulder

The board shoulder type you pick affects your final deck appearance by influencing your fastener selection.

Think about whether you’d prefer a fastener-free surface to one that features visible screw heads or plugs — remember, the primary reason for choosing grooved composite decking is so you can use hidden clip fasteners.

Get the Look You Want With Grooved or Square-Shoulder Boards

Choose square-shoulder or grooved composite decking for a fastener-free surface

For a Fastener-Free Surface

Choose hidden clip fasteners with grooved composite deck boards or Cortex top-down fasteners hidden by plugs with square-shoulder, full-profile boards.

Choose square-shoulder over grooved composite decking for top-down fasteners

For Visible Color-Matched Screws

TOPLoc® Color-Matched Screws blend in with your deck surface thanks to painted screw heads. They are compatible with grooved boards and square-shoulder boards.

Get More Details About Hidden Fastener Options

Learn about hidden fasteners options for both square-shoulder and grooved composite deck boards.

Use square-shoulder over grooved composite decking for perimeter boards

Finish Your Edges With Square-Shoulder Boards

You’ll also want to think about your deck perimeter — will board edges be visible? Even if you choose grooved boards for your deck surface, use square-shoulder boards for your stairs and perimeter for a nice clean edge.  

Solid vs Grooved Composite Decking: See Your Options Up Close

Grooved composite decking works best with hidden clip fasteners for grooved composite deck boards

Now that you know the differences between composite deck board shoulder types, you’re ready to start exploring your deck board color options. Order free samples of your favorite TimberTech decking colors to see our nature-inspired decking up close.

See & feel the TimberTech advantage

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

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