How Many Decking Pedestals Should You Require For Your New Deck?

If you’re planning to install a composite deck using decking pedestals then the number that you require will depend on many factors. The factors include the size of the deck, the types of joists and boards you’re using, and the manufacturer’s instructions.

Fortunately, working out how many you’ll need is fairly straightforward and shouldn’t take much time.

In this guide, we’ll take a look at what decking pedestals are, how to properly install them, and show you how to figure out how many you’ll need for your decking project.


What Are Decking Pedestals?

Decking pedestals, also known as risers, are adjustable, plastic supports that are placed underneath decking boards. The specific properties of decking pedestals vary depending on the manufacturer but below we have given some typical specifications.

  • They’re generally frost-resistant to -40˚C and heat-resistant to 60˚C.
  • They are usually made of polypropylene.
  • They have a resistance to chemical cleaning products.
  • They can be laid on most surfaces such as grass, bitumen and gravel.
  • They can typically support 1000 kg in weight or more.
  • They have an adjustable height which can go as high as 260 mm on some models.


Why Should I Use Decking Pedestals?

Access and drainage

In commercial buildings, if deck boards are laid over the top of certain utilities such as water pipes these will need to be accessible. Using decking pedestals means that the composite decking boards can easily be lifted when access is required.

A deck or terrace will also need to be provided with adequate drainage. As decking boards can be laid directly onto decking pedestals without any grouting being required water can easily find its way in between the boards or tiles.

Foot traffic

Your deck terrace is likely to experience heavy footfall during its lifespan and it’s very important that it’s able to withstand this. It may also need to be able to bear the weight of heavy furniture and ornaments.

Most decking pedestals are made using polypropylene which is a very strong material. This means that each pedestal will provide proper support to your decking area and reduce the risk of any boards collapsing.

During the installation of your decking, you should check the manual provided by the pedestal manufacturer to see what the load-bearing capability of the pedestals is.


When installing your deck you may find that there is unstable or uneven groundwork. This would usually require you to create a sub-frame in order to support the decking. Constructing and laying this timber frame could cause delays in your decking project.

If you use a decking pedestal with joist supports or advanced spacer tabs you can avoid having to construct a sub-frame altogether. You can simply adjust the pedestals to the desired height and begin laying your decking boards on top of them.

Concrete foundations

As decking pedestals can be placed directly onto the ground you don’t need to lay concrete foundations before you start installing your deck terrace. You just need to lay out the pedestals, position the joists, and then attach the deck boards.


How To Install Decking Pedestals

1) Prepare the ground

Decking pedestals can be placed directly onto any type of surface such as concrete, tiles, or bare earth. Before you begin installation you’ll need to check that the surface is level by using a spirit level so that the risk of the surface shifting is low.

If you’re installing onto bare earth then a floating installation will probably be necessary. This is when the weight of the deck boards holds the structure down to the ground.

You can allow some minor irregularities in the surface but it should mostly be perfectly flat. Be sure that you check with a spirit level multiple times before you begin.

When installing directly onto bare earth you will need to either lay a fine concrete screed or a geotextile membrane to help prevent weed growth once the boards have been laid.

2) Pedestal spacing

You’ll next need to take measurements and decide what the overall height of your decking will be. If there are any doors that need to be factored in then you’ll need to decide if you want the decking to be flush with it or if you need to install steps.

You’ll then need to work out how many pedestals will be required for the job. Usually, the decking manufacturer will indicate how many are needed per metre squared.

Finally, you need to decide which direction your boards will go as this will determine how you will space out your pedestals.

3) Installing the pedestals

Now, start laying out the pedestals with the correct amount of spacing that you have decided on. If required, secure them with specified attachments or fixing plugs. Then, adjust them to the right height.

You should always leave a slight slope away from your property to encourage water drainage.

The spacing in between your risers will depend on the boards and joists that you use and you should always check the instructions from the manufacturer before you begin.

Generally, there shouldn’t be more than 70cm between consecutive decking joists.

4) Laying the joists

Next, you’ll need to start screwing the joists onto the pedestals so that the joists form a right angle with how your deck boards will be laid. Be careful that you don’t cause any damage to the adjustable mechanisms of the pedestals as you do this.

As a rule, you should aim to leave at least 10 cm between the boards and the ground to allow for proper ventilation.

5) Laying the deck boards

The next stage is to lay the decking boards over the joists and then attach them. You can do this by using screws or fasteners. Our composite decking boards come with hidden fasteners to preserve the visual appeal of the boards.

If you are using screws then make sure that you pre-drill the holes to reduce the risk of the boards cracking or splitting when the screws are attached.

6) Trimming

Once all of the boards have been laid and securely attached you can then start to trim them if necessary. It’s best to do this all in one go at the end rather than trimming them as you go.

To trim the ends of the boards you should use a circular saw.

7) Fixing miscalculations

If you’ve made any miscalculations with your measurements then you may need to remove certain boards and adjust their length or width. Again, you should use a circular saw to do this.

Once the boards have been adjusted you’ll need to lay them on top of the joists again. For any boards that have had their widths adjusted it’s best to lay them on the facade side of the deck to hide them from view.



How much space should I leave in between composite deck boards?

Generally, you should leave between 3mm and 6mm of space in between each composite board. This is to allow enough room for the boards to contract and expand during temperature fluctuations.

If you don’t leave enough room then this could cause friction when the boards expand and could lead to unsafe gaps when they contract. Although composite doesn’t expand and contract as much as wood it will still do so during high and low temperatures.

Should I seal my composite deck?

There is no need to seal composite products as they are naturally resistant to water and rot. This means that moisture doesn’t penetrate into the core of the boards and rot is unable to form. If you choose to seal composite boards then it’s best to use lumber wax.

Is a composite deck eco-friendly?

Composite is considered to be the most eco-friendly decking option as it’s made with reclaimed wood and recycled plastics. Our range of composite boards is made with 95% recycled material and FSC-certified wood.


Browse Through Ecoscape’s Amazing Range Of Composite Deck Boards Today

Once you’re ready to start installing your composite deck take a look at our exciting range of composite boards. Our Clarity range boards come with a 20-year warranty and the boards in our Forma range come with a 25-year warranty.

There’s also a wide range of contemporary colours for you to choose from so that you can find something that’ll perfectly complement your home. All of our boards are scratch-resistant, water-resistant, UV-resistant and much more.

So, browse our range and order your free quote or sample today.

Gary is the founder and CEO of Ecoscape UK. Gary graduated from Liverpool JM University in 2007 with a 2:1 in Economics. A passion for innovation, design and sustainability, Gary has put to market numerous wpc products/systems, some of which have UK and European registered designs. Outside of work Gary enjoys spending time with his family, the great outdoors and watching Manchester United.