Installing composite decking is within reach of anyone, even without extensive DIY experience. This guide takes you through the process step by step: choosing the right base, installing the joists and boards, cutting, steps and finishing. With the Quick-Fix system (just one screw per board), installation is up to 3 times faster than with a traditional deck.
Do not install below 5°C, in humidity above 90%, or in snowy conditions.
Acclimatisation
Store the boards flat at the installation site for at least 48 hours, protected from bad weather and direct sunlight.
Base
The surface must be flat and stable, with a minimum drainage slope of 5 mm/m running in the same direction as the joists and boards.
Ventilation
The space between the boards and the ground must never be obstructed, and water must not be allowed to collect, particularly inside the boards.
Installation and warranty
Use CDECK accessories only and follow the instructions in this manual. Failure to do so will invalidate the warranty.
Tools and materials
To install your CDECK deck, you will need:
CTOOL (CDECK installation template)
Rubber mallet
Drill
Screwdriver / drill driver
Circular saw fitted with a wood-cutting blade
Tape measure
Spirit level (recommended for checking that the surface is level)
Latest version of the CDECK Technical Datasheet
Step 1
Installation types
The type of base determines the installation method. CDECK supports three installation types.
Type 1
Level base (screw-fixed)
Type 2
Uneven base (screw-fixed)
Type 3
Raised and/or non-drilled installation
Watch the video on installation types
Which installation type is right for my base?
Find your type of base in the table below to identify the correct installation method.
Your base
Installation type
In brief
Concrete slab or solid cement base that is level and can be drilled
Type 1
PVC joists fixed to the ground and fully supported along their length.
Base that can be drilled but is uneven or at different levels
Type 2
Structural aluminium joists, with a maximum span of 500 mm.
Waterproof membrane or compacted surface that cannot be drilled
Type 3
Cross-braced structure using aluminium joists and tubes fixed to one another.
Surface that needs to be raised
Type 3
Cross-braced structure combined with height-adjustable CDECK pedestals.
Soft ground or soil
Type 3
Compacted support areas, geotextile membrane and a cross-braced structure using aluminium joists and tubes fixed to one another.
Watch the installation-on-soil video
Step 2
Installing the substructure
The joists form the base of your deck and are fixed to the ground using screws and plugs.
Key points
Joist spacing: maximum 400 mm for residential use and 350 mm for commercial use.
Support: at least 3 joists per board; 2 joists at every board-to-board end joint.
Gap between joists: leave 3 to 5 mm between joist ends to allow water to drain.
Gap from fixed elements: at least 20 mm from walls and other fixed elements.
Fixing: screws spaced a maximum of 500 mm apart for PVC joists or 600 mm for aluminium joists.
Step 3
Installing the boards
Once the substructure is in place, you can install the boards. Each board is secured using terminal clips at the ends and intermediate clips along the centre.
Key points
Fixing: use just one screw per board, on the clip closest to the centre, positioned at 60° using the CTOOL.
Intermediate clips: the standard clip is suitable for most installations; the Pro clip allows an individual board to be removed later, which is useful for maintenance or access to services.
End-to-end board gap: minimum 6.5 mm between two boards.
Gap from fixed elements (walls): minimum 15 mm.
Overhang: maximum 50 mm between the end of a board and the nearest joist.
These gaps are essential. Composite expands and contracts with changes in temperature and humidity. Without the correct spacing, the boards may warp or break.
How do you cut composite decking boards?
To cut boards to size, use a circular saw fitted with a wood-cutting blade. Wear appropriate personal protective equipment, work outdoors or in a well-ventilated area, and always cut on a stable surface.
Step 4
Steps
The CDECK step profile creates a continuous transition between different levels. Installation follows the same principles as the rest of the deck, with a few adjustments.
Key points
Horizontal joist: position it 65 mm from the step edge to maintain the required 6.5 mm gap between boards.
Required gaps: 20 mm from fixed elements and 6.5 mm between boards.
Fixing: use terminal clips at the beginning and end of the step, with intermediate clips for the step profile itself.
Step 5
Finishing
Two accessories can be used to finish exposed edges: finishing trims — or closure boards — and, for hollow boards, end caps.
Key points
Finishing trims: glue in place using wood/PVC adhesive and secure with screws, using one screw per board. They can be installed parallel or perpendicular to the board depending on the application.
End caps: fit these before installing the boards. First drill the underside of each board to ensure proper drainage.
Removing and replacing a board
The Pro intermediate clip allows you to remove an individual board without dismantling the entire deck — useful for maintenance or for accessing services underneath.
Key points
With Pro clips: unlock the clip using the CTOOL, remove the board, then refit it and lock the clip again.
Without Pro clips: around the edge of the deck, simply remove the terminal clips. For boards in the middle, cut the intermediate clips with an angle grinder and reinstall the board using Pro clips.
What about cleaning?
After installation, some cutting dust may remain on the boards. An initial clean with fresh water, a mild detergent and a soft brush is enough to leave the surface clean.
The most common mistakes are installing boards without the correct expansion gaps, failing to secure the joists, or mixing accessories from different systems. Find out more in our dedicated article: the most common mistakes when installing a composite deck.
Can composite decking boards be installed directly on the ground?
No. An air gap between the boards and the ground is essential and is created by the Quick-Fix joists.
Do the joists need to be fixed, or can they simply be laid in place?
The joists must always be fixed either to the ground or to other profiles forming a secured structure, in accordance with the Technical Datasheet.
Can composite decking be installed directly over soil?
Yes, using a secured Type 3 structure, with compacted ground in the support areas and an unobstructed air gap beneath the deck, for example using a geotextile membrane.
Can the boards be installed without gaps between them?
No. The specified gaps must always be respected: at least 6.5 mm between board ends and 15 mm from fixed elements. Without sufficient spacing, the deck may warp, lift or break.
How many screws are needed per board?
Just one, installed on the clip closest to the centre of the board at a 60° angle using the CTOOL. Never screw the clips directly to the joists.
Can I use accessories from other decking systems?
No. CDECK is designed and tested as a complete system. Only CDECK accessories should be used; otherwise, the warranty may be invalidated.
Can a DIYer install CDECK?
Yes. Anyone with some DIY experience and the right tools can install CDECK by following the Technical Datasheet and installation videos.
Do the boards need to acclimatise before installation?
Yes. Leave them at the installation site for at least 48 hours before fitting, and do not install below 5°C or when humidity exceeds 90%.
Have a question or an unusual installation?
For any situation not covered in this guide — or if you would prefer to have your deck professionally installed — contact us.
How to install composite decking
Installing composite decking is within reach of anyone, even without extensive DIY experience. This guide takes you through the process step by step: choosing the right base, installing the joists and boards, cutting, steps and finishing. With the Quick-Fix system (just one screw per board), installation is up to 3 times faster than with a traditional deck.
Explore all our composite decking boardsBefore you start
Before beginning installation, make sure you have the latest version of the CDECK Technical Datasheet and Installation Manual, and read both carefully in full.
Weather conditions
Do not install below 5°C, in humidity above 90%, or in snowy conditions.
Acclimatisation
Store the boards flat at the installation site for at least 48 hours, protected from bad weather and direct sunlight.
Base
The surface must be flat and stable, with a minimum drainage slope of 5 mm/m running in the same direction as the joists and boards.
Ventilation
The space between the boards and the ground must never be obstructed, and water must not be allowed to collect, particularly inside the boards.
Installation and warranty
Use CDECK accessories only and follow the instructions in this manual. Failure to do so will invalidate the warranty.
Tools and materials
To install your CDECK deck, you will need:
Installation types
The type of base determines the installation method. CDECK supports three installation types.
Level base (screw-fixed)
Uneven base (screw-fixed)
Raised and/or non-drilled installation
Which installation type is right for my base?
Find your type of base in the table below to identify the correct installation method.
Installing the substructure
The joists form the base of your deck and are fixed to the ground using screws and plugs.
Key points
Installing the boards
Once the substructure is in place, you can install the boards. Each board is secured using terminal clips at the ends and intermediate clips along the centre.
Key points
These gaps are essential. Composite expands and contracts with changes in temperature and humidity. Without the correct spacing, the boards may warp or break.
How do you cut composite decking boards?
To cut boards to size, use a circular saw fitted with a wood-cutting blade. Wear appropriate personal protective equipment, work outdoors or in a well-ventilated area, and always cut on a stable surface.
Steps
The CDECK step profile creates a continuous transition between different levels. Installation follows the same principles as the rest of the deck, with a few adjustments.
Key points
Finishing
Two accessories can be used to finish exposed edges: finishing trims — or closure boards — and, for hollow boards, end caps.
Key points
Removing and replacing a board
The Pro intermediate clip allows you to remove an individual board without dismantling the entire deck — useful for maintenance or for accessing services underneath.
Key points
What about cleaning?
After installation, some cutting dust may remain on the boards. An initial clean with fresh water, a mild detergent and a soft brush is enough to leave the surface clean.
Cleaning and maintenance guideFrequently asked questions about installation
What installation mistakes should I avoid?
The most common mistakes are installing boards without the correct expansion gaps, failing to secure the joists, or mixing accessories from different systems. Find out more in our dedicated article: the most common mistakes when installing a composite deck.
Can composite decking boards be installed directly on the ground?
No. An air gap between the boards and the ground is essential and is created by the Quick-Fix joists.
Do the joists need to be fixed, or can they simply be laid in place?
The joists must always be fixed either to the ground or to other profiles forming a secured structure, in accordance with the Technical Datasheet.
Can composite decking be installed directly over soil?
Yes, using a secured Type 3 structure, with compacted ground in the support areas and an unobstructed air gap beneath the deck, for example using a geotextile membrane.
Can the boards be installed without gaps between them?
No. The specified gaps must always be respected: at least 6.5 mm between board ends and 15 mm from fixed elements. Without sufficient spacing, the deck may warp, lift or break.
How many screws are needed per board?
Just one, installed on the clip closest to the centre of the board at a 60° angle using the CTOOL. Never screw the clips directly to the joists.
Can I use accessories from other decking systems?
No. CDECK is designed and tested as a complete system. Only CDECK accessories should be used; otherwise, the warranty may be invalidated.
Can a DIYer install CDECK?
Yes. Anyone with some DIY experience and the right tools can install CDECK by following the Technical Datasheet and installation videos.
Do the boards need to acclimatise before installation?
Yes. Leave them at the installation site for at least 48 hours before fitting, and do not install below 5°C or when humidity exceeds 90%.
Have a question or an unusual installation?
For any situation not covered in this guide — or if you would prefer to have your deck professionally installed — contact us.
Contact us