Composite decking joists & support beams
Our joists and support beams are made from composite wood for strong, durable decks that are built to last.
Quality substructures for safe, strong decks
The long-term performance of any commercial decking installation relies heavily on the structural integrity of its subframe. Specifying the correct joist and beam network is critical to maximising the safety, load-bearing capacity, and overall lifespan of the project.
Manufactured and rigorously tested at our Scunthorpe facility, our composite joists and beams ensure your substructure meets strict commercial requirements and remains fit for purpose in demanding environments.
Why choose composite joists and support beams?
Composite wood joists and support beams provide a highly durable, low-maintenance alternative to traditional timber substructures. Engineered for exceptional weather resistance and heavy-duty use, they will not rot, splinter, or warp over time.
Crucially for commercial applications, composite profiles effectively withstand rising damp, ensuring the specified deck boards above remain fully protected regardless of challenging site conditions.
Understand the structural advantages of a composite subframe by reading our technical article: Why choose a composite subframe over timber?
Composite decking joists and beams from Ecodek
Browse our Low Profile support beams and deeper profile Superstiff joists below. For advice on choosing the right beam or joist for your deck, please get in touch.
Low profile support beams
Our low profile beams (also known as ‘decking bearers’) will support a wide range of composite and timber decking components.
They’re ideal for installations with a low distance from the ground, although we recommend no less than 100mm.
Overview:
- Profile: 40mm x 48mm
- Colour: Black
- Can be used with our pedestals or heavy duty support posts
- Made from composite wood to combat rising damp and protect the decking above
- Will not rot, splinter, or warp
- Should be supported by pedestals or packers at every 500mm intervals or less
For more information about these deck support beams, please download the product sheet and technical data sheet.
Superstiff deep profile joists
For decking on raised outdoor dining areas, leisure areas and balconies, our Superstiff deep profile joists are the best option.
Available in five colours, they suit both composite and timber decking components.
Overview:
- Profile: 38mm x 88mm
- Colour options: Black, Dark Brown, Light Brown, Dark Grey, Light Grey
- Can be used with our heavy duty support posts or pedestals
- Recommended to use alongside our Superstiff screws (6.5 x 80mm carbon steel screw) for extra security
- Made from composite wood to protect the decking above by combating rising damp and won’t splinter, rot, or warp
- Should be supported by pedestals or packers every 1000mm or less – please refer to our installation guide for more support: Joist spacing for composite decking requirements
Find more information about our Superstiff joists by downloading the product sheet and technical data sheet.
Talk through your requirements
Unsure of which joists and beams or other accessories you need for your substructure? We’re here to help. Our team of decking experts are happy to talk through your options and answer any questions you have.
Making outdoors, yours
Installation support
All the information and support you need to install your composite decking is here on our website.
Ecodek insights
Check out our recent articles
Looking to learn more about composite decking accessories and components? Visit our blog for the lowdown.
Composite joist and support beam FAQs
What size composite joists for decking should I use?
It’s important you choose the right size composite joists to ensure your deck subframe is safe, strong, and built to last. We supply joists in two sizes to meet the needs of different decking applications:
- 38mm x 88mm Superstiff deep profile joists
Supports composite and timber decking on raised outdoor dining areas, leisure areas, and balconies
- 40 x 48mm Low Profile decking bearers
Ideal for a wide range of composite and timber decking components with a low distance from the ground
Our team is here to help you find the joist size that’s right for your deck. Please call us on 01978 667 840 or use our contact form to get in touch.
What is the best joist spacing for composite decking?
The distance between each joist underneath your deck is known as ‘joint spacing’. Each deck’s joist spacing is different, but the importance is the same. Get the spacing right and your deck will be solid and structurally sound for years to come. Get it wrong and you open up a realm of safety vulnerabilities.
The best spacing for composite deck joists depends on the size, shape, and weight of the decking they’re supporting. For example, our Low Profile composite joists should be fitted at no more than 500mm intervals, whereas our Superstiff joists at no more than 1,000mm intervals. A composite decking expert will be able to advise you on the right distance to leave between joists for your deck.
Always follow the manufacturer’s installation instructions when fitting your joists with the correct spacing. For detailed guidance on joist spacing, please read our blog: Joist spacing for composite decking requirements.
Visit our help & advice pages for more technical product information and support.