What Can I Lay My Decking Base On?

When you build a deck, it’s essential to consider which decking support materials will best suit its base. You want to ensure it remains level and stable while withstanding the weight of the deck.

The choice of materials has much to do with the height of the deck and what surface you’ll be mounting the deck onto. It is crucial to select a suitable decking base that provides stability and durability for your deck, ensuring that it lasts for many years.

How Far Apart Should My Decking Supports Be?

The spacing of your decking pedestals or other supports depends on several factors. You’ll need to consider the size, weight and type of your decking material and your joist size and spacing. Here are some guidelines to assist with spacing your decking supports:

Decking material weight

The weight of your decking material impacts how far apart you space your decking pedestals or other supports. Heavier materials will likely need to be spaced closer together to prevent any sagging or potential collapse.

Joist size and spacing

The size and length of the joists you use are defined by the weight of the load that the deck will carry and also the design of the deck. The spacing of the joists for Ecoscape composite decking products should be no bigger than 400mm centre to centre.

What Should I Use as a Decking Support?

Support structures for composite and timber decking, along with other decking types, will typically include wood or 100% plastic beams, posts and joists. Steel and aluminium support structures are also well-utilised.

Fixed and adjustable pedestal support is commonly used as support pads for decking. These allow for a completely free-standing system without the need for concreting. Some materials often used for decking support purposes are:

Composite: Composite materials, such as composite posts, beams, and joists, are also available for the support structure of a composite deck. These materials are made from recycled plastic and wood, providing a durable and low-maintenance option.

Aluminium: Aluminium is a well-known option used for decking support structures. It is anti-corrosive, lightweight and easy to work with.

Pressure-treated wood: Wood is a common choice for the support structure of decks, especially for timber decking. It is an available, durable and cost-effective option.

Steel: Steel beams, posts and joists are often used as decking support structures due to their strength and durability. They also offer resistance to insects, dampness and other environmental factors.

Be sure to choose materials that are suitable for outdoor use that will support the weight of the deck and the live load it will carry.

What Products are Available?

There are several products available for composite decking support, including:

Decking pedestals

Ecoscape supplies several decking pedestal options. These allow you to level your deck’s surface and provide an affordable, eco-friendly option for supporting your new deck. Whether using timber decking or Ecoscape’s wide range of quality composite products, our fixed or adjustable pedestal options will simplify your deck erection.

We manufacture pedestals with 100% recycled Polypropylene. They have a 50-year design life and include a 15-year limited warranty, and you’ll have no environmental concerns if you use our pedestals.

We offer King dual adjustable and Queen adjustable fixed pedestal options in a variety of different sizes. Ecoscape’s adjustable pedestal tools are utilised in small to large residential and commercial projects, so you can be sure they’ll provide sturdy decking support for all heavy decking.

Visit the Ecoscape decking pedestal webpage for further information on these products. You’ll find their specifications and access to a handy pedestal calculator there too.

Plastic decking posts

Ecoscape 100% recycled plastic posts are 100 x 100mm posts that are three metres long. They create a maintenance-free composite decking substructure that provides sturdy decking support.

These Ecoscape plastic posts are available in dark brown, but you can request black as an option as well. They are splinter-free, weather-resistant and easy to install. Each comes with the Ecoscape 25-year warranty.

Plastic and aluminium decking joists

At Ecoscape, we offer a range of timber-free decking substructure solutions through 100% recycled plastic and aluminium joists. These provide durable and eco-friendly decking solutions with 25-year warranties included. Ecoscape also carries a spectrum of battens perfect for your cladding projects.

If you’re looking for a substructure that won’t warp, rot or weaken in time, Ecoscape’s joists, battens and posts are perfect for your needs. These provide a maintenance-free solution that utilises our hidden fixings system.

What is a Deck Joist?

A deck joist is a horizontal structural component that provides decking support to the boards by transferring their weight to the ledger board or beams of a deck. Joists are typically constructed of composite plastic or wood and installed at right angles to the beams or ledger board. They run parallel to each other and are spaced at regular intervals.

Joist Decking Span and Spacing

So you know, the joist span is the total length of your joist from end to end. The spacing is the distance between each individual joist measured from the centre of one to the centre of the one adjacent to it (CTC). Ideally, deck joists should be spaced 300 to 400mm apart (CTC). As a rule, leave a minimum of 10 cm between the joists and the ground for ventilation purposes.

What Should I Lay My Decking Base On?

When laying composite decking, or timber decking for that matter, your decking support should be a flat, stable base. It needs to support the deck’s weight of the deck and any live load it carries. Decking pedestals provide this as they’re adjustable support pads aligned specifically to ensure a perfect deck installation.

A pedestal adjusts to sit on several different base support pads. You could place them on concrete, gravel and hard standing areas. Certain pedestals, like the Ecoscape Queen pedestals, take extension pieces that allow you to create various height pedestals with a maximum height of 1500mm.

How to Construct a Decking Substructure

When you’re considering a substructure for your decking, first determine the height and location of your deck. Mark your selected area off with stakes and string. If it is a raised deck, consider concrete footings at regular intervals and on the corners of the perimeter.

Alternatively, you can make use of pedestals to support the composite or timber joists you’ll be utilising.

Place any posts or columns on your footings, ensuring they are level and plumb. Place beams on top of the posts, and fit your joists perpendicular to the beams, spacing them at regular intervals as detailed earlier. Use appropriate fixings to secure the joists to the beams. Make use of a ledger board if needed. This board attaches to the house to support the joists on one side.

What Are the Best Fixings for Decking Joists?

You should ideally use stainless steel, high-quality coated A4 countersunk wood or masonry screws, or clips that are specifically designed for composite decking to fix the boards. It’s better not to use traditional screws or nails as they could split or damage the decking material.


What is decking support?

Decking support refers to the structural foundation and support structure for a deck. It is typically made of 100% plastic materials or timber.

How do I choose the right type of decking support?

Suitable decking support will depend on several factors, including the size and shape of the installation. The deck’s height and weight are also important, as is the condition of the soil below the erected platform.

How do you support raised decking?

Raised decking is supported by beams, posts or footings, or a combination of them. You can also use decking pedestals and extension pieces, where necessary, like the ones we supply at Ecoscape, to do the job.

Should plastic posts be concreted?

Plastic decking posts can be concreted into the ground to a depth of 600mm – depending on the height of your deck and the ground conditions. Another option is to fix them down to a metal support plate which should be anchored down to a concrete pad or footing. For further details on the construction of plastic substructures please visit our website.

Final Thoughts

Try to find out as much as you can about the installation of your project and which decking support system will be best to ensure its durability and stability. At Ecoscape UK, we offer environmentally friendly and low-maintenance alternatives to timber decking. These come with warranties allowing you the peace of mind that your deck will stand the test of time.

You might require further information or advice on decks and their support before making your final decision. Have a look at our composite decking installation guide, and feel free to contact us with any questions you may have.

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.