Installing composite decking is within reach of anyone with some DIY experience. This guide takes you through it step by step: choosing the installation type, fitting the joists and boards, cutting, steps and finishing trims. With the Quick-Fix® system, which uses just one screw per board, installation is up to 3 times faster than with traditional decking.
Don’t install in temperatures below 5 °C, humidity above 90 % or snow.
Acclimatisation
Store the boards flat on site for at least 48 hours, protected from rain and direct sunlight.
Base
The surface must be flat and stable, with a minimum fall of 5 mm per metre for drainage, in the direction of the joists and boards.
Ventilation
The space between the boards and the ground must never be blocked, and water must not be allowed to stand, especially inside the boards.
Installation and warranty
Only use CDECK accessories, in line with the manual. Failure to do so voids the warranty.
Tools and materials
To install your CDECK decking, you will need:
CTOOL (CDECK installation tool)
Rubber mallet
Drill
Screwdriver
Circular saw with a wood blade
Tape measure
Spirit level (recommended for checking levels)
Up-to-date CDECK Technical Data Sheet
Step 1
Installation types
The type of base determines the installation method. CDECK offers three types:
Type 1
Even base (screw fixing)
Type 2
Uneven base (screw fixing)
Type 3
Raised and/or drill-free installation
Which installation type should I choose for my base?
Your base
Type
In short
Even, drillable concrete slab or screed
Type 1
PVC joists fixed to the ground, supported along their full length.
Drillable but uneven or sloping base
Type 2
Structural aluminium joists, max. span 500 mm.
Waterproofing membrane or compacted ground (not drillable)
Type 3
Crossed structure of joists and aluminium tubes, fixed to each other.
Floor to be raised
Type 3
Crossed structure combined with height-adjustable CDECK® plots.
Soil or loose ground
Type 3
Compacted ground, geotextile membrane and a crossed structure of joists and aluminium tubes, fixed to each other.
Step 2
Installing the joists
Quick-Fix joists, also known as battens, form the base of the decking and are fixed to the ground with screws and wall plugs.
Key points
Joist spacing (centre to centre): max. 400 mm for residential use, 350 mm for commercial use.
Board support: at least 3 joists per board; 2 joists at each end-to-end joint.
Gap between joists: 3 to 5 mm between the ends, for water drainage.
Gap to fixed elements: at least 20 mm (walls, etc.).
Fixing: screws every 500 mm maximum (PVC) or 600 mm (aluminium).
Step 3
Installing the boards
Once the structure is in place, lay the boards. Each board is fixed with an end clip at each end and with intermediate clips.
Key points
Fixing: a single screw per board, in the clip closest to the centre, at 60° using the CTOOL.
Intermediate clips: the standard clip is suitable for most installations. The PRO clip lets you remove a single board later, which is useful for maintenance or to reach drains and inspection chambers.
End gap: minimum 6.5 mm between two boards.
Gap to fixed elements (walls): minimum 15 mm.
Distance to the joist: maximum 50 mm between the end of the board and the nearest joist.
These gaps are not optional. Composite expands with temperature and humidity and, without them, the boards can warp, lift or crack.
How do I cut composite decking boards?
To trim the boards to size, use a circular saw with a wood blade. Wear personal protective equipment, work outdoors or in a well-ventilated space and cut on a stable surface.
Step 4
Steps
The CDECK® Step creates a seamless transition between levels. Installation follows the same principles as the rest of the decking, with a few adjustments.
Key points
Horizontal joist: 65 mm from the front of the step, to keep the 6.5 mm gap between boards.
Gaps to keep: 20 mm to fixed elements, 6.5 mm between boards.
Fixing: end clips at the start and end of the step, intermediate clips on the step piece itself.
Step 5
Finishing trims
There are two accessories for finishing the sides: fasteners and, on hollow boards, end caps.
Key points
Fasteners: glued (wood/PVC adhesive) or screwed, with one screw per board. Fitted parallel or perpendicular to the board, as required.
End caps: fitted before the boards. First drill the underside of each board to ensure drainage.
Removing and replacing a board
The intermediate PRO clip lets you remove a board without taking up the whole deck, which is handy for maintenance or to reach drains and inspection chambers.
Key points
With a PRO clip: unlock it with the CTOOL, remove the board, put it back and lock it again.
Without a PRO clip: at the edges, simply remove the end clips. In the middle, cut the intermediate clips with an angle grinder and reinstall with PRO clips.
What about cleaning?
After installation, it’s normal for some cutting dust to remain on the boards. A first clean with water, a neutral detergent and a soft brush is enough to leave the surface clean.
The most common are installing the boards without expansion gaps, not fixing the joists and mixing accessories from other systems.
Can I lay the boards directly on the ground?
No. An air gap between the boards and the ground is essential, and this is provided by the Quick-Fix joists.
Do the joists have to be fixed or can I just lay them down?
They must be fixed. The joists must be fixed to the ground or to other profiles that form a braced structure, as set out in the Technical Data Sheet.
Can I install decking directly over soil?
Yes, as long as you use a braced structure (Type 3), compact the ground where the supports sit and keep the air gap under the decking clear, for example with a geotextile membrane.
Can I install the boards without gaps (butted together)?
No. You must keep to the gaps specified: minimum 6.5 mm between board ends and 15 mm to fixed elements. Without them, the decking can warp, lift or crack.
How many screws does each board need?
Just one, in the clip closest to the centre, driven at 60° using the CTOOL. Never screw the clips to the joists.
Can I use accessories from other systems?
No. CDECK was designed and tested as a complete system. Only install it with CDECK accessories, otherwise the warranty will be void.
Can I install the decking myself?
Yes. Anyone with some DIY experience and the right tools can install CDECK by following the Technical Data Sheet and the videos.
Do the boards need to acclimatise before installation?
Yes. Leave them on site for at least 48 hours before installing, and don’t install in temperatures below 5 °C or humidity above 90 %.
Have a question or a specific case?
If your situation isn’t covered in this guide, or if you’d prefer to have your decking installed by professionals, talk to us.
How to install composite decking
Installing composite decking is within reach of anyone with some DIY experience. This guide takes you through it step by step: choosing the installation type, fitting the joists and boards, cutting, steps and finishing trims. With the Quick-Fix® system, which uses just one screw per board, installation is up to 3 times faster than with traditional decking.
Before you start
Before you start installing, make sure you have the latest version of the CDECK Technical Data Sheet and Installation Manual and read them carefully from start to finish.
Weather conditions
Don’t install in temperatures below 5 °C, humidity above 90 % or snow.
Acclimatisation
Store the boards flat on site for at least 48 hours, protected from rain and direct sunlight.
Base
The surface must be flat and stable, with a minimum fall of 5 mm per metre for drainage, in the direction of the joists and boards.
Ventilation
The space between the boards and the ground must never be blocked, and water must not be allowed to stand, especially inside the boards.
Installation and warranty
Only use CDECK accessories, in line with the manual. Failure to do so voids the warranty.
Tools and materials
To install your CDECK decking, you will need:
Installation types
The type of base determines the installation method. CDECK offers three types:
Even base (screw fixing)
Uneven base (screw fixing)
Raised and/or drill-free installation
Which installation type should I choose for my base?
Installing the joists
Quick-Fix joists, also known as battens, form the base of the decking and are fixed to the ground with screws and wall plugs.
Key points
Installing the boards
Once the structure is in place, lay the boards. Each board is fixed with an end clip at each end and with intermediate clips.
Key points
These gaps are not optional. Composite expands with temperature and humidity and, without them, the boards can warp, lift or crack.
How do I cut composite decking boards?
To trim the boards to size, use a circular saw with a wood blade. Wear personal protective equipment, work outdoors or in a well-ventilated space and cut on a stable surface.
Steps
The CDECK® Step creates a seamless transition between levels. Installation follows the same principles as the rest of the decking, with a few adjustments.
Key points
Finishing trims
There are two accessories for finishing the sides: fasteners and, on hollow boards, end caps.
Key points
Removing and replacing a board
The intermediate PRO clip lets you remove a board without taking up the whole deck, which is handy for maintenance or to reach drains and inspection chambers.
Key points
What about cleaning?
After installation, it’s normal for some cutting dust to remain on the boards. A first clean with water, a neutral detergent and a soft brush is enough to leave the surface clean.
How to maintain composite deckingInstallation FAQs
What mistakes should I avoid when installing?
The most common are installing the boards without expansion gaps, not fixing the joists and mixing accessories from other systems.
Can I lay the boards directly on the ground?
No. An air gap between the boards and the ground is essential, and this is provided by the Quick-Fix joists.
Do the joists have to be fixed or can I just lay them down?
They must be fixed. The joists must be fixed to the ground or to other profiles that form a braced structure, as set out in the Technical Data Sheet.
Can I install decking directly over soil?
Yes, as long as you use a braced structure (Type 3), compact the ground where the supports sit and keep the air gap under the decking clear, for example with a geotextile membrane.
Can I install the boards without gaps (butted together)?
No. You must keep to the gaps specified: minimum 6.5 mm between board ends and 15 mm to fixed elements. Without them, the decking can warp, lift or crack.
How many screws does each board need?
Just one, in the clip closest to the centre, driven at 60° using the CTOOL. Never screw the clips to the joists.
Can I use accessories from other systems?
No. CDECK was designed and tested as a complete system. Only install it with CDECK accessories, otherwise the warranty will be void.
Can I install the decking myself?
Yes. Anyone with some DIY experience and the right tools can install CDECK by following the Technical Data Sheet and the videos.
Do the boards need to acclimatise before installation?
Yes. Leave them on site for at least 48 hours before installing, and don’t install in temperatures below 5 °C or humidity above 90 %.
Have a question or a specific case?
If your situation isn’t covered in this guide, or if you’d prefer to have your decking installed by professionals, talk to us.
Talk to us