A flawless outdoor deck will provide the stage for great performances. Like any stage, this one needs the right supporting player: the sub-frame. While it might not get the same star treatment as your choice of surface finish, using the right sub-frame is key to a long-lasting and durable deck.
With a range of sub-frame options available, the decision-making process needs to consider technical performance, compliance and ease of installation.
Fit for Purpose
Whether you’re creating a peaceful residential veranda or a bustling commercial terrace, the core sub-frame system remains largely the same consisting of joists and joist supports attached together to form a level frame upon which deck boards can be securely fixed.
The sub-frame design will most likely vary depending on the anticipated use. Higher footfall areas typically require closer joist spacing to maintain structural integrity. It’s an engineering consideration and our technical team are well-placed to provide the necessary information as most systems will recommend specific joist centres for the end application.
Looking at the location
Ground-level installations offer the most flexibility in terms of choice of finish material, however if the system is to be installed directly onto the ground, a timber base frame will be required.
Entirely bespoke, and therefore able to accommodate any shape and size with ease, our Timber in Ground system uses Southern Yellow Pine, one of the strongest softwoods on the market. Once the In Ground system is in place, it can be combined with a metal or timber sub-frame to support the required surface finish.
If installing on a hard standing such as a concrete base at ground level, combining a timber sub-frame with Buzon Pedestals provides millimetre-precise slope correction, great load bearing and full height adjustability. Any of our wood or metal subframe systems will be appropriate, with the choice often dictated by the system and surface finish specified.
As the height of the project goes up, so does the level of regulation around material choice.
Compliance with Fire Regulations
Regulations for balconies on residential buildings over 11 metres in height require all components to be Class A1 or A2 fire rated. For these installations, a non-combustible sub-frame system combined with an appropriately rated surface finish would be required.
Our Zerodeck system is a good example of a compliant build up. With a choice of finishes in porcelain or mineral composite, it has a natural timber aesthetic and when paired with Buzon A-PED pedestals and joists, provides a fully adjustable, non-combustible system perfect for anywhere requiring maximum fire-safety.
This roof terrace, providing a view of St Paul’s Cathedral in London is a great example of Zerodeck Composite. While Class A fire rating is not required for all buildings, many specifiers prefer to opt for this degree of fire safety even in low rise or non-residential buildings.
The regulations for roof terraces are different to those relating to balconies, with the highest classification for roofs being BROOF(t4). The major difference is that the full build up – from membrane through to the surface finish – must be tested together and certified as an integrated system; individual components cannot be switched or replaced, and importantly sub-frames need to be paired with specific surfaces and membranes to be compliant.
The Outdoor Deck Company supply a number of finishes that have been tested with specific build ups that include Buzon polypropylene pedestals and roof systems from leading roofing manufacturers. These finishes include Zerodeck Porcelain, Zerodeck Composite and Silver FR. Please contact us for more information.
Technical Compatibility
In many instances the choice of sub-frame will be dictated by the surface finish specified. For example, the Grad Hidden-Fix System uses an invisible, clip-based system for fast, screw-free installation and a flawless finish. The success of this design requires joists that are supplied pre-mounted with clips that click into grooves cut on the underside of compatible surface boards, ensuring perfect spacing and alignment every time.
The Grad system includes a wide range of timber finishes and can also be used with Buzon Pedestals for technical or commercial installations. See this example of a Grad Hidden-fix deck on an office building in central London.
Alternatively the Silvadec system, robust enough for high-traffic commercial projects but also perfect for domestic situations, has deck boards composed of a highly slip-resistant and durable wood composite, and uses a side-clip fixing that integrates with the Silvadec aluminium joist and accessories. This system can be installed directly on pedestals or the aluminium joists can be fixed to a timber frame.
More than a sum of its parts
In summary, the choice of sub-frame is essential to achieve the performance and finish required – a choice that sometimes involves technical input and an understanding of the precise regulatory requirements.
Decking design should always be approached as a system, as the best result will always be achieved when the correct components are specified to work in harmony. Our team is on hand to provide advice and support to ensure the appropriate combination of materials is specified.
If you would like to discuss which system is appropriate for your decking project, speak to one of our experts today.
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