Decking Pedestals

Your joist pedestals must be installed on a prepared, untreated ground surface or a concrete slab. We strongly advise against installing them directly on soil without stabilisation, due to the risk of settlement or ground movement caused by weather conditions (rain, drought) or the weight of the structure. Whether you are installing your pedestals on an unfinished ground surface or a concrete slab, the surface must be clean, stable and properly levelled to ensure a durable and secure decking.

Each pedestal type has its own specific installation method. To ensure you follow the correct installation steps, we recommend you read the installation guide for the pedestals you have chosen for your project.

However, we can summarise the installation of decking pedestals in a few simple steps:

• Preparing the ground: preparing the ground is essential before starting your project. On a concrete slab, you must ensure that the surface is clear of any obstacles to ensure your pedestals are properly stabilised. On natural ground, make sure to properly level and compact the ground. To do this, remove the topsoil to a depth of approximately 15 cm, then lay a geotextile before creating a base layer of 0/31.5 crushed stone. For best results, compact the entire surface using a vibrating plate. Proper levelling ensures the durability of your decking area.
• Position the pedestals: install the pedestals following the layout plan and recommended spacing. The pedestals must be laid evenly and with the appropriate spacing (around 70 cm). Use a spirit level to check that each pedestal is level.
• Install the joists and wooden boards: start by adjusting the height of your pedestals. For a wooden or composite deck, secure the joists to the pedestals using suitable screws. You can then lay your decking boards, fixing them to the structure.
• Final adjustments: check the alignment and stability of the entire structure. Make any necessary adjustments to ensure a uniform and safe surface. Don’t forget the edges of the patio, which you can also finish to ensure a clean, modern look.

For detailed and specific instructions, we recommend consulting the installation guides provided on the product page of the pedestal you are using. They contain precise information and illustrations to guide you step by step.

The spacing between the pedestals will depend on the type of wood and the cross-section of the joists you are using. As a general rule, we recommend a distance of 70 cm between each adjustable pedestal. For joists, we recommend a centre-to-centre distance of 50 cm if your decking is made of natural wood boards. Please note that these guidelines differ for a composite decking.

Here are the steps to follow to estimate the number of pedestals you will need to build your wooden or composite decking.

First, measure the area of your decking and draw up your installation plan, considering the recommended spacing for your flooring material.

To know the recommended spacing between each pedestal, please refer to the relevant installation guide, available on the product page for the decking pedestal you are using, and the advice from your wood manufacturer.

To calculate the number of pedestals:

• Divide the length of the deck by the recommended spacing between two pedestals, then do the same with the width.
• Multiply the two results to obtain the total number of pedestals required.
• Remember to add extra pedestals for edges, corners or specific cuts.
• Always round up to the nearest whole number for optimum stability and keep a few spares in reserve.

For further details, please refer to our practical guide to calculating decking pedestals.

Jouplast® decking joist pedestals have a crush test resistance of over 1 tonne. However, the weight that a raised decking can support depends not only on the strength of the pedestals and whether they have a high load resistance, but also on the type of wood used for the decking. We therefore advise you to consult your timber supplier for more precise information on this matter.

More generally, if you are planning to place a heavy item on your raised decking, such as a hot tub for example, we recommend our PROFILDECK® solution (aluminium joists), which will allow for better weight distribution across the subframe structure of the installation.

Jouplast adjustable decking pedestals are durable and come with a 10-year warranty, subject to our terms and conditions of sale and in accordance with our directions for use.  They are UV-resistant and frost-resistant and have a weight tolerance of up to 1 tonne per pedestal. This makes them a robust and stable support.