If you’re looking to build a decking project that is going to stand the test of time, the subframe of a decking area is one of the most important parts. Whilst the subframe is generally hidden, it is crucial for the deck’s longevity.

A poor subframe choice or install can lead to the decking being damaged or can even lead to the decking becoming structurally dangerous and eventually failure.

With so many different subframes to choose from, which one is best and what should you look out for? Here, Millboard look at three options:

Timber

Softwood timber is the most common material used for decking subframes. Due to the natural properties of timber, it is important to ensure the correct Use Class is purchased. Timber subframes should be clear of the ground and must have an airflow ventilation gap around the outside, and a free air space across the whole underside of the frame that will not impede the free flow of air.

• Timber is easy to work with
• Generally readily available
• Naturally a strong product with a high strength-to-weight ratio
• When correctly specified and installed, timber subframes can have a long service life
• Many examples have failed within six years of being installed
• Not all treated timber is suitable – they can have very different classifications and be designed for use in different locations
• Prone to rotting

Plas-Pro (recycled plastic)

Plas-Pro is made from 100% recycled plastic. By using selected graded materials and cleverly engineered processes, Plas-Pro provides key environmental benefits and the assurance of superior quality performance.

• Strong, versatile and easy to work with
• Available in a range of sizes to act as posts, joists and bearers
• Never rots, even when placed in water
• Can be used to create unique and special outdoor constructions, incorporating curves and twists that would be impossible with conventional materials
• Unlike timber, Plas-Pro can be used in contact with the ground and in water without the need for any airflow ventilation gaps
• Can be cut, drilled, fixed into and bolted
• Slight differences in relation to colour, texture, temperature, and dimensional variations are possible
• An expansion distance (expansion joint) must be maintained during installation
• Should not be stored in direct sunlight to avoid material deformation
• Plastic doesn’t have the same strength-to-weight ratio as timber therefore will need more support

DuoSpan® (aluminium hybrid)

DuoSpan provides the perfect subframe for Millboard decking and as well as a universal support system for other outdoor flooring options. Its ingenious design facilitates top-down fixing of decking boards and makes it an easy installation for all levels of competence.

• Quick and easy to install
• Joists are resistant to rotting or moisture ingress
• Flexible brackets means components can be connected at almost any angle
• Screw-locating grooves on the side of the joists and self-drilling screws ensure fast, consistent fitting
• The self-drilling screws provided with the brackets are made from A4 marine-grade stainless steel and they are coated in a cathodic barrier coating
• Complies with Eurocode 1: Actions on Structures (BS EN 1991-1-1)
• Achieve increased spans of up to 1.8m and can cantilever up to 600mm (Please refer to our loading tables for the full lists of spans in the required locations)
• Requires coating in highly alkaline or acidic areas
• Where the DuoSpan joists and beams are placed in direct contact with concrete, a protective layer is required
• Avoid putting DuoSpan aluminium components in contact with other metals, as increased galvanic corrosion could occur

In conclusion, timber, recycled plastic (Plas-Pro) and aluminium (DuoSpan) subframes all have different attributes and being familiar with the benefits of each and knowing what to use and when can add years to the deck’s longevity.

For further information on any of the points listed above, download Millboard's Guide to Decking Subframes for an in-depth analysis to help you make an informed decision.

Need some more help, or not sure what subframe to go for? Get in touch with Millboard’s Technical team who will be happy to help. Reach them at 024 7643 9943.