What Subframe is best for Composite Decking – The Ultimate Guide 2023

March 2023
Armani Eagle

If you are looking at using composite decking in your garden, you’ve made a great choice! It’s extremely durable, easy to maintain, and has great aesthetic appeal – this is why it’s become increasingly popular in the UK over the last few years, it’s the perfect material to stand up to whatever British weather is thrown at it.

To ensure that your decking is installed exactly to your needs and wants, it is very important to select the best subframe material to install your composite decking on. Choosing the correct subframe will affect the longevity of your deck just as much (if not more) that the actual decking material itself.

The subframe is like the foundation of your decking area, it’s the part no-one usually sees, but plays a vital role in terms of the decks overall stability and longevity. In this Article, we will look at the 5 different types of composite decking subframes and go into more detail about the pro’s and con’s of each, so you can decide which decking subframe material is best for your garden project.

What are the different materials used for Decking Subframes?

  1. Aluminium Subframes
  2. Steel Subframes
  3. Plastic Subframes
  4. Composite Subframes
  5. Timber Subframes


  1. Aluminium Subframes

Aluminium Decking subframes are made from extruded aluminium joists, which are then connected together to form one of the most, if not the most, long lasting decking subframes. They are very simple to install, and consist of a few components that are all designed for maximum lifespan. These include:

  • Aluminium Joists
  • Joist Connectors (to connect joists together at corners and along straights)
  • Plastic Pedestal Supports
  • Self-Drilling Screws, to make construction extremely simple

Aluminium decking subframes are usually used in combination with support pedestals, which are adjustable to give you a perfectly level subframe. OVAEDA offers a 25 year warranty on all its aluminium decking subframes, due to that fact we are so confident in the materials and components outlasting that by far. Perfect for damp environments, Aluminium decking subframes will not rust or rot – they are not affected by water in any way! They also don’t expand and contract, meaning that once your aluminium decking subframe has been installed, it’ll still feel just as solid 20 or 30 years down the line.

An Aluminium Decking Subframe is one of the best alternatives to a timber subframe, as its benefits far outweigh its slightly increased initial cost. For a start, it’ll outlive timber, and in normal circumstances, will last 2 or 3 times as long! It also doesn’t warp or bow, unlike timber, which will be affected dramatically by varying conditions.

Explore the Ovaeda range of Aluminium Decking Subframes

Pros of an Aluminium Subframe

  • Extremely Long Lasting
  • Low maintenance – once installed, no maintenance is needed
  • Easy to work with – aluminium is easy to cut, using a chop saw with a multipurpose blade
  • Cost Effective – Long term, this decking subframe materials is one of the cheapest

Cons of an Aluminium Subframe

  • Initial cost can be higher than other decking subframe materials

Aluminium Decking Subframe

  1. Steel Subframes

Pre-Made Steel Subframes are becoming an increasingly popular option for composite deck areas throughout the UK - this is due to their large number of benefits. Ovaeda’s Pre-Made Steel Subframes are made from light gauge steel c-section, which is then made into large format panels, before it is delivered to site to be constructed in a matter of hours. Steel decking subframes are the fastest install method, its just a case of supporting the frames correctly on pedestals, fixing them together, and installing your decking on top.

As I’m sure we all know, steel is a very hard material, so is supplied with special self-drilling screws that mean fixing your decking down is simple.

Pre-made steel subframes are some of the strongest structurally, and are galvanized to stop rust – this means that steel subframes are also very long lasting – OVAEDA offers a 10 year warranty on all our steel subframes.

Pros of a Steel Subframe

  • Quickest install method by far
  • Durable material that is not affected by Rot
  • Structurally one of the sturdiest options

Cons of a Steel Subframe

  • Not as versatile as some decking subframe materials
  • Initial cost can be slightly higher than other decking subframe materials

Steel Decking Subframes

  1. Plastic Subframes

Plastic decking subframes are another popular material being used to construct composite decks.

Plastic subframes are comprised of solid plastic joists, that are then directly fixed together and constructed on site.  They are usually made from recycled plastic, making them an eco-friendly option.

Plastic decking subframes come in different thicknesses, making them a versatile option that can be used in a number of different circumstances.

Explore the Ovaeda range of Plastic Decking Subframes

Pros of a Plastic Subframe

  • They don’t rot, they are resistant to water
  • Relatively simple to install
  • Eco-friendly

Cons of a Plastic Subframe

  • Can sag over time – plastic is not the strongest decking subframe material out there, so will have to be bulked up to maximise its lifespan.
  1. Composite Subframes

Composite Decking Subframes are comprised of similar materials to that of a composite deckboard. They are made of a combination of wood fibres, plastic, and a bonding agent. Generally speaking, they are not the longest lasting subframe option out there, it is the most likely to sag.

The reason for this is that it has wood fibres in the joist (like the deckboard itself) However because the subframe has much less sunlight, it is a far damper environment than that of the deckboard itself. This can cause composite joists to take in water over time, making them expand, contract and warp – not something you want with a subframe!

Pros of a Composite Subframe

  • Relatively Cheap
  • Less susceptible to rot than timber
  • Easy to install

Cons of a Composite Subframe

  • Not the strongest decking subframe option
  • Can rot over time in damp environments


  1. Timber Subframes

Timber decking subframes have been one of the most popular options due its cheap initial cost, and the fact that it is very easy to get hold of. However, it does have the shortest lifespan of all decking subframe materials listed. This is because it is very susceptible to rotting – as we have mentioned further up, subframes are usually fairly damp, especially in the UK, meaning that the timber will always be affected by water in some way – timber decking subframes usually only last 5-10 years before they need replacing.

Timber decking subframes are usually consisted of large-format timber joists, that are then spaced throughout your decking area, and directly fixed together using timber screws. It is very easy to install, and most tradesman or DIYers will have no issue constructing a timber subframe.


Pros of Timber Subframe

  • Easy to install
  • Cheapest Initial costing subframe option generally

Cons of a Timber Subframe

  • Will rot very quickly
  • Very High Maintenance

 Timber Decking Subframe

How long will a timber subframe take to rot?

As we’ve mentioned further up, a timber subframe is very likely to rot. However, there are some ways to prolong the decay, and depending on the timber used and method of installation, you can increase the lifespan of your subframe.

Firstly, the dampness of the area dramatically affects the lifespan of your timber subframe. In a deck area which has little access to sunlight, the atmosphere will be much damper, as the sun can not dry it out. Sometimes, this can mean that if an untreated timber was used, it’d only last around 2-3 years. A drier area that has access to sunlight for most of the day will fare better as far as how long it takes to rot.

Constantly maintaining your timber subframe is a great way of delaying rot, however this can be very time consuming. Painting the ends of all joists upon installation, and coating the joists will increase the lifespan, however, this removes one of the main benefits of a timber subframe, which is its ease of install, and increases its cost.

Rot spreads once it has begun growing on the timber, even if it does not have external access to moisture after its initial growth – it’ll spread by using any moisture in the timber itself. A way to further delay rot on a timber subframe is the remove its contact with the ground. A way of doing this is to use a decking support pedestal – this will help prevent some of the moisture accessing the wood and spreading further. Installing pedestals with your timber subframe can increase its lifespan by a few years.

Should timber subframes be avoided?

Where possible we’d recommend avoiding a timber subframe. It has the shortest lifespan when compared against aluminium, steel, plastic, and composite subframes. Its disadvantages with its short lifespan and constant maintenance in order to keep it in good condition for outweigh its initial cost saving. Over time, a timber subframe can be more costly and time-consuming than other subframe materials like aluminium, as it may need to be replaced.

OVAEDA specialises in aluminium, steel, and plastic subframes, and many of our clients come to us to replace their rotting timber subframe – all materials we offer will significantly outlive a timber decking area, assuming that they are installed correctly.   

How to choose the best Composite Decking Subframe for your project

Now that we’ve had a deeper dive into each subframe material, you will need to make a decision on what the best composite decking subframe material is for you. Take your time to think about your requirements – are you looking for a long-lasting solution, or is it a more temporary, initially cheaper solution that you require?

Subframe Material Price

Depending on the subframe you choose, your subframe cost can vary quite a bit. Working out roughly how many joists you require, and pulling together some quotes for each will help you to begin budgeting.

One thing to bear in mind, is that it is not just the initial cost that you’ll have to bear in mind when deciding on the best subframe for your area. Timber subframes will need replacing every 5-10 years, so if you are looking to have your decking area in place for 30 years or so, you could look at multiplying the initial cost by 3 for a fair comparison to other longer lasting subframe materials like aluminium, which will not need replacing once installed.

Subframe Durability

Another very important factor to consider when choosing the best composite decking subframe for your deck area is the durability.

In general:

  • Aluminium Subframes last 30+ Years
  • Steel Subframes last 10-25 years
  • Plastic Subframes last 10-15 years
  • Composite Subframes last 10-15 years
  • Timber Subframes last 5-10 years (even less in some circumstances)

We’d always recommend choosing a decking subframe material that lasts at least as long as your composite deck board. Depending on the composite decking you’ve selected, the lifespan will vary. OVAEDAs composite decking boards are extremely durable, lasting upwards of 20 years. Our Natura and Luxxe Composite Decking Ranges even have a 25 year warranty to back this up!

Subframe Ease of Instal

Depending on the decking subframe material you select, the simplicity of install can vary dramatically. It is definitely something worth considering, as a shorter install time reduces installation time, and therefore costs.





















Ease of Install






Overall Score







Getting started with your Composite Decking Subframe

Now that you’ve got a deeper understanding as to the different materials that are used for composite decking subframes, hopefully you can make a more informed decision as to the best one for you.

OVAEDAs specialists would be extremely happy to help you with working out the quantity of joists required, along with helping out with frame drawings, and supplying the materials. Contact us to start the process of building your decking area!