When the time comes to choose composite decking, one of the most common questions is exactly this: should I go for a hollow or a solid board? To answer it, you need to understand the differences between the two types, what the market offers and the situations in which each one makes sense.

Not all composite decking is the same

Before comparing hollow and solid composite decking, there is an essential point that is often overlooked: not all composite decking is of the same quality.

With most composite decking on the market — especially products made from polyethylene (PE) or polypropylene (PP) — hollow boards are not recommended in any situation, because the mechanical strength of these products is usually very low.

That is why the choice between hollow and solid only really matters when the product is of a high enough quality for both versions to be reliable.

CDECK composite decking beside a swimming pool, Chocolate colour

What are hollow and solid composite decking boards?

The difference between the two types lies in the board’s internal structure.

A hollow composite decking board has air chambers inside it — the so-called hollow cores — which reduce the board’s weight and allow some internal ventilation.

A solid board is completely solid, with no air chambers. It has more mass and, in certain conditions, greater impact resistance.

Cross-section of a hollow composite board
Hollow boardair chambers, lighter
Cross-section of a solid composite board
Solid boardsolid, more resistant

CDECK Original hollow and solid boards

CDECK Original® is composite decking available in hollow and solid boards, manufactured in the EU. Both share the same dimensions (2300 × 140 × 24 mm), the same 6 colours and the same installation configuration — which means they can be combined within the same project.

Unlike most products on the market, the CDECK hollow composite decking board is stronger than many of the solid decking boards available on the market. The mechanical strength of decking made from polyethylene (PE) or polypropylene (PP) is typically much lower than that of CDECK.

CDECK Original® Hollow Board

Advantages

  • More affordable — it uses less raw material.
  • Heats up less in the sun — the air chambers allow internal ventilation, resulting in lower surface temperatures under direct sunlight. A real advantage around swimming pools or in regions with hot summers.
  • Suitable for most residential and commercial projects.
Disadvantages
  • Lower impact resistance than the solid version.

CDECK Original® Solid Board

Advantages

  • Greater resistance to impact and knocks.
  • Less dimensional variation with humidity and lower water absorption — more stable in permanently humid environments.
Disadvantages
  • Higher price — the result of the larger volume of raw material used.
  • Heats up more in the sun than the hollow version — its greater mass and smaller exposed area result in higher surface temperatures under direct sunlight.

Technical comparison

The data below is taken from the official CDECK Original Declaration of Performance (DoP) and lets you compare the technical performance of the two versions.

CharacteristicHollow BoardSolid Board
Flexural strength (EN 310)53 N/mm²58 N/mm²
Impact resistance +23 °C / 1 kg (EN 477)15.5 J> 20 J
Impact resistance −10 °C / 1 kg (EN 477)9.5 J> 20 J
Water absorption (EN 15534-1)5.5%1.9%
Thickness swelling (EN 15534-1)2.3%1.1%

Note: IHT allows for a 30% variation due to the production process and exposure to climatic factors.

CDECK composite decking beside a swimming pool, Grey colour

When does a solid board make sense?

With CDECK Original, solid composite decking is only justified in very specific situations:

Extremely cold environments — locations where temperatures can drop below −20 °C.
Environments with extreme, permanent humidity — such as saunas or indoor swimming pools with constantly high temperature and humidity.
Risk of total or partial submersion — environments or areas with a high risk of the boards being totally or partially submerged, or where water is likely to get inside the hollow cores.
Areas likely to face heavy mechanical impacts — for example, hospitality areas where beer kegs, gas cylinders and the like are unloaded.

Choosing between hollow and solid composite decking is not a question of one being better than the other — it is about matching the solution to the real conditions of the project. For the vast majority of applications, the hollow version of CDECK Original offers everything you need. The solid version exists to meet truly demanding conditions.

CDECK® Composite Decking

With a warranty of up to 25 years for residential use and up to 10 years for commercial use, CDECK is available in two ranges: CDECK Original®, in hollow and solid versions, and CDECK WUUDE®, with a capped finish that recreates the authentic look of natural wood.

Simulate your deckCDECK® Composite Decking