How Much Does A Decking Subframe Cost?

March 2022
Anton White

A decking subframe is one of the most important aspects to consider asides the actual decking itself. After all, they are the two main components that make up a deck area, right? In terms of durability, it is VERY important that you understand the durability of the materials, as if the material doesn’t last long, you will have to replace them, potentially doubling the cost of your subframe in the long term. 

Cost is a significant factor and probably at the forefront of your decision making when deciding what subframe would be best for your decking area. Everyone will have various budgets, sizes and requirements for their deck areas.

With any of the materials discussed, the larger the deck area, the more materials required, and this usually also pushes up the cost not per sqm, but overall, so we ask you to bear this in mind.

In this article, I will go through the four main subframe materials and explain the costs involved in each, so that you can decide the best subframe material for you.



Wooden joists are very readily available from most DIY shops, meaning the cost of this material is relatively low. It costs around £7.50 per linear meter for a structural wooden joist. A simple 30sqm deck area would use around 130 linear meters of joist, meaning it would cost around £1000-£1200 for the subframe materials excluding supports. Once you add supports for the joists, the total cost of your subframe would be in the region of £1400-£1600. You will also have to bear in mind that a wooden subframe usually lasts around 5-10 years before rot, twisting and warping get the better of it. It is at this point that you will have to look at replacing it. So over a 25 year period, a wooden subframe could cost you £3000-£4000, or £100-£125 per square meter. Installation for a wooden subframe is simple and can be done by a homeowner or a professional installer. A professional installer would be able to complete a wooden subframe relatively quickly, however they come at a price. An average landscaper would cost you £200-£400 per person, per day.



Aluminium is a more durable material and slightly harder to purchase from regular DIY shops, meaning it is more expensive. As it is the strongest and most durable product on this list, it will last you around 25 years with little to no maintenance at all. It can cost around £12 per linear meter for a high strength aluminium joist, however as it won’t warp like timber, it does not require noggins so less material is required. A simple 30sqm deck area would use around 110 linear meters of joist, meaning it would cost around £1400-£1600 for the subframe materials including fixings. This also excludes the supports. Aluminium subframe systems are usually designed to work along with a plastic pedestal support, which also last a long time. A 30sqm decking area would use around 100 pedestals, making the total cost of the subframe in the region of £1600 - £1800. Over a 25 year period, an aluminium subframe will remain the same price as when initially purchased, as it should not need replacing. As with wooden decking, you could also use an installer for an aluminium subframe. However, this is not essential as aluminium is also fairly simple to work with.


As composite joists are comparatively weak, meaning they have the lowest price per linear meter. Composite joists cost around £5 per linear meter. As with timber, noggins are required to ensure that it does not bow or warp. A simple 30sqm deck would use around 130 linear meters of joist, meaning it would cost around £850 including fixings for the subframe materials. This excludes any supports, which is where the cost would increase because of the quantity of them required. The problem with composite decking joists is they will require a lot of support if you want to make sure that they wont sag too badly. It is never a good sight when you can see a decking is sagging and peaking, as this is usually because the joists do not have the correct support. You would need at least 250 supports to properly support a composite subframe. Usually this is done in the way of pedestals, which will cost you from £500-£700, bringing the total cost for a 30sqm composite subframe to around £1400-£1600. It has the potential to not last as long as 25 years, so you may need some maintenance in the mean time to ensure that it supports your decking as long as possible.



Plastic joists have similar properties to wood but are much more expensive. They cost around £13 per linear meter. A simple 30sqm deck area uses around 130lm so would cost around £1800 including fixings and excluding supports. Supports are also very expensive, costing over £20 per linear meter. Once you have 100 supports at 300mm long, it will end up costing you £500-£700 for the supports alone. Add it all up and a plastic subframe support for your decking will cost £2300 - £2500 for a 30sqm area. Roughly £80 per square meter. As it is plastic, it will not biodegrade so will in effect last up to 25 years, however it may sag and warp too badly before this. If this does happen, it may be necessary to replace the subframe.



What Now?

Now that I have gone over some costings of each material, you should have gained an understanding as to what frame is going to work with you. Here at OVAEDA, we specialise in an aluminium subframe system, so we are obviously going to think that is the best option for you, and we truly believe that!

However it is your choice. I have tried to be as unbiased as possible, and have sourced all pricing from popular websites that supply these products.

How would I purchase an Aluminium Subframe?

If you are interested in the possibility of using an aluminium subframe for your new decking area, please get in touch! Anyone you get in touch with here at OVAEDA will be more than happy to help, sort you out with samples, a quote, or even just answer any technical questions you may have. Call us on 0208 159 2999 or email us at

Oh, and have you checked out our other blogs? Click here

We have a wealth of information regarding all things garden that you may want to have a look at before finalising your decisions.