It is one of the first questions that comes up: hollow or solid decking? And it usually comes with the same assumption — that hollow decking is the cheaper option and solid decking is the better one. It is not that simple. Here, we explain what changes inside the board, what the market offers and when each option makes sense.
Before looking at the profile, look at the quality of the composite
This is the point that is often overlooked, and it matters more than the choice of profile: not all composite decking is made to the same standard.
For most products on the market, particularly those made from polyethylene (PE) or polypropylene (PP), hollow boards are not recommended for any application. The reason is that these products often have relatively low mechanical strength. To put it into perspective, their strength is typically between 25% and 50% of that of CDECK.
So, the choice between hollow and solid only really matters when the product itself has the quality needed to make both versions reliable.
The difference is inside the board
From the outside, they look the same. What changes is what is inside.
A hollow composite decking board has internal air chambers, or hollow sections. This reduces the weight of the board and allows some internal ventilation.
A solid board is solid from one side to the other, with no internal chambers. Its greater mass can provide higher impact resistance under certain conditions.
The two CDECK Original® board options
CDECK Original® is a composite decking range with both hollow and solid boards, manufactured in the European Union. Both versions have the same appearance and dimensions: 2300 × 140 × 24 mm, the same six colours and the same installation system. This means they can be combined within the same project.
And here is the point that challenges the usual assumption in the market: the CDECK hollow board is more resistant than many solid composite decking boards currently available.
Hollow board
Advantages
- Lower cost, because it contains less raw material.
- Stays cooler in direct sunlight. The internal air chambers allow air to circulate within the board, helping to keep the surface temperature lower under direct solar radiation. This is particularly noticeable around swimming pools and in any outdoor space exposed to strong summer sun.
- Suitable for most projects, both residential and commercial.
- Lower impact resistance than the solid board.
Solid board
Advantages
- Higher impact and shock resistance.
- Lower water absorption and less dimensional change caused by moisture, making it better suited to permanently humid environments.
- Higher cost, because it contains significantly more material.
- Gets hotter in direct sunlight than the hollow version. Its greater mass and lower exposed surface area mean higher surface temperatures under direct solar radiation.
The numbers, side by side
These figures are taken from the official Declaration of Performance (DoP) for CDECK Original®.
| Test | Hollow board | Solid board |
|---|---|---|
| Flexural strength (EN 310) | 48 N/mm² | 57 N/mm² |
| Impact resistance at +23 °C (EN 477) | 80 cm without breakage | 200 cm without breakage |
| Impact resistance at −10 °C (EN 477) | 100 cm without breakage | 200 cm without breakage |
| Resistance to point load (EN 1533) | 6,810 N | 8,780 N |
| Water absorption (EN 317) | 1.1% | 0.6% |
| Thickness swelling (EN 317) | 0.4% | 0.3% |
Note: IHT considers a 30% variation due to the manufacturing process and exposure to climatic conditions.
When does the solid board really make sense?
For CDECK Original®, solid composite decking is only justified in four scenarios:
It is not about one being better than the other. It is about choosing the solution that genuinely suits the conditions of the space.
For the vast majority of projects, the hollow version of CDECK Original® provides everything you need. The solid version exists to meet truly demanding conditions.
And if one area of your space is subject to more wear than the rest, remember that you do not have to choose just one: both versions share the same dimensions, colours and installation system.
The solution
CDECK, composite decking for outdoor spaces
Manufactured in the European Union and backed by a warranty of up to 25 years, CDECK is available in two ranges: CDECK Original®, in hollow and solid versions, and CDECK WUUDE®, with an encapsulated finish that recreates the authentic appearance of natural timber.
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