Hollow vs. Solid Composite Decking: The Tradesman’s Truth

The Evolution of Hollow Composite Decking

Hollow composite boards feature internal channels running the length of the board to reduce weight and cost. Today, they primarily come in two profiles: square hollow and circle hollow.

Years ago, square hollow boards earned a poor reputation. Some manufacturers pushed 4-square hollow boards that were under 20mm thick. In a domestic setting, these thin boards regularly failed within just 5 years. The industry has learned from this. Here is where the market stands now:

When researching on installing composite boards right, you will inevitably run into the debate between hollow and solid composite boards.

There is a lot of noise online, but the tradesman’s truth is simple: both are great products, but they have very different benefits and disadvantages depending on their application.

To give you the bottom line upfront: hollow composite is perfect for domestic gardens, while solid composite is engineered for commercial spaces. Below, we break down exactly why.

Feature	4-Square Hollow (22mm)	Circular Hollow	Solid Core
Lifespan	Up to 10 Years	Up to 15 Years	20+ Years
Joist Centres	300mm (Strict)	300mm	More forgiving
Impact Resistance	Standard domestic	Superior shock distribution	Maximum / Commercial grade
Best Application	Budget residential	Premium residential	Commercial / Heavy loads

Square Hollow Boards

The 22mm Standard: A 4-square hollow board is now standard at 22mm thick. At this thickness, it is good enough to last a solid 10 years in a garden. Upgrading to a 5-square hollow board will easily surpass that lifespan.
Joist Centres: If you use a 4-square 22mm board, your joist centres must be strictly set at 300mm. If you anticipate extra weight (like large planters), you will need to reduce that centre spacing even further.
<b”>Water Management: Excess water trapped inside any hollow board has the potential to freeze and crack the plastic. While this is rare, it makes building your subframe with a slight gradient essential for drainage.

Circle Hollow Boards

Circle hollow boards use slightly more material, making them denser than square profiles. This gives them a lifespan of up to 15 years.

The Science: Without boring you with the physics, circular geometry distributes impact shock waves much better than square corners. This gives circular hollow boards vastly superior impact resistance.

The Verdict on Hollow: They are cheaper, they will stand the test of time, and they are the absolute perfect fit for residential projects.

Solid Composite Decking: Built for Commercial Strength

Solid boards are incredibly dense, strong, and heavy. This extra mass is exactly what makes them the go-to choice for commercial projects and heavy-duty environments.

Forgiving Strength: Solid boards hit massive flexural bending strengths, often achieving ratings of 36 to 45+. Simply put, they are incredibly forgiving under immense, continuous weight.
Longevity: Because of the solid core, these boards can easily last well over 20 years. Even if they sustain minor surface cracks from extreme commercial wear and tear, their structural integrity remains completely intact.

Which Board Should You Choose?

If you are upgrading your family garden or building a standard patio area, hollow composite decking is the smartest choice. It delivers the weather resistance you need at a fraction of the cost.

However, if you are designing a public commercial space or a deck that will house incredibly heavy structures, solid composite decking is worth the premium upgrade.

Ready to find your perfect match? Browse our full range of composite decking boards to get started today.

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