In short, yes! Composite Decking can be laid on concrete AS LONG as you have the correct sub-frame to do so, normally joists. Not sure what that means? Then this blog will most certainly help.
It's really important that you lay your composite decking correctly on a suitable sub-frame. Unfortunately incorrect installation of your sub-frame can lead to long-term problem with your decking and in most cases installation on an incorrect sub-frame will invalidate any warranty you have which is the last thing you want.
In this blog we are here to help guide you in the right direction and give you helpful tips on how to install your decking boards and sub-frame correctly on to concrete.
Note: Please be aware that this is only a guide and the instructions outlined may not be suitable for every project. We strongly recommend speaking to a professional and getting personalised advice for your specific project before laying and building any sub-frames, if you are not qualified, or have no previous relevant experience.
As we mentioned earlier, your decking should always be installed on a flat and stable base. Decking boards must NEVER be laid directly on the ground but instead should be fixed to joists of a suitable sub-frame. In most cases we recommend installing your Alpha Composite Decking on a solid concrete base using plastic composite joists. Whilst we recommend our Alpha Composite joists, as an alternative subframe option - plastic, timber or metal joists can also be used.
Some common issues to be aware of with your concrete patio include:
The concrete base should be at least 100mm thick and have a slope with a decline of 1% - 1.5% that runs away from the property to aid drainage and the run-off of water that may collect under the decking. Tip: You may also want to add 6mm-8mm drainage holes the depth of the base every 4-5m2 to aid drainage.
Spacing - A gap of at least 10mm should be left between the ends of joists and any fixed object such as a walls. Where double joists are required, a gap of 3mm should be left between the 2 joists that lay next to each. Double joists are required where 2 board ends will meet (butt-joins) see picture 6 ahead. Where 2 joist ends meet (butt-joins) an expansion gap of 8mm should be left.
We recommend that the maximum space between joist rows should never exceed 300mm. Note, boards laid diagonally should be support by joists spaced no more than 250mm apart. Each board cut should be support by a minimum of 3 joists.
To begin attaching the joists to the concrete base, start off by pre-drilling holes in the centre groove of your joists. Your first fixing should be approximately 60-70mm from the joist edge. Continue along the joist screwing at 500mm intervals using a drill bit of sufficient length to create a secure fixing. Expansion screws may be needed. Tip: For extra support and longevity we advise using noggins between joists.
Your sub-frame is now ready for your decking boards to be laid. You can download our full installation guide here to learn how to lay your decking boards correctly.
Remember, if you need any further helps, tips or advice please feel free to get in touch where we'll be more than happy to help.
Are you ready for the next step? Use our FREE composite decking cost calculator to work out exactly how much you'll need for you project.