Decking can be a wonderful addition to any home, extending your living space into the outdoors and providing the ideal setting for relaxation and entertainment. 

Decking requires a frame to support it and traditionally, that frame would be fashioned from timber. But metal frames are rising in popularity due to their many benefits.

Would a metal frame be the best choice for your decking project?

What are metal frames for decking?

All areas of decking should be laid on a subframe. That frame ensures that the completed deck is stable, level, of the required height and adequately drained. 

Frames are commonly constructed from treated softwood or hardwood. But it is possible to utilise a metal frame constructed from aluminium or steel. 


What are the benefits of metal frames?

Metal frames deliver many benefits that are worth considering before you invest in a subframe for your decking:

Durability and Longevity

Unlike wooden frames, metal frames are impervious to rot, mould, and insect damage. This resistance significantly extends the lifespan of the decking structure. Indeed, metal frames can last up to 4 times longer than timber frames.

Metal frames can also withstand harsh weather conditions, including heavy rain, snow, and extreme temperatures, without warping, cracking, or deteriorating.

Strength and Stability

Metal frames, particularly those made from steel or aluminium, offer superior strength compared to wood. This structural integrity supports greater loads and delivers frames that can span larger areas without requiring additional support.


Both steel and aluminium provide uniformity and consistency in construction, ensuring that every piece fits precisely as designed, reducing the likelihood of errors during installation or an uneven finish.

Low Maintenance

Metal frames require little maintenance. Timber frames need sealing, staining, or painting regularly to maintain their appearance and integrity.

Most metal frames are coated with protective finishes to retard corrosion, further reducing the need for ongoing maintenance.

Environmentally friendly

Metal frames can be made from recycled materials and are recyclable at the end of their lifespan, contributing to environmental sustainability. They do not require chemical treatments to prevent decay and insect infestation and so are more environmentally friendly options.

Contemporary aesthetics

Providing a sleek, contemporary look, metal frames complement modern architectural styles. They can be paired with various decking materials, including wood, composite and synthetic options, to achieve the desired aesthetic.


Both aluminium and steel are non-flammable materials unlike timber. If your decking could be used for barbecues, flammability is a consideration.

Can house plumbing and cables

Plumbing and electrical cables can be housed safely within metal frames, and frames can be installed directly over hard-landscaped areas without disturbing any existing utilities.


Metal frames enable you to choose from a variety of decking materials including wood, PVC and composite boards.

Help you to get creative

Timber decks are generally square or rectangular in shape or may feature interconnected square and rectangular sections. Metal frames enable you to get creative with your decking design as they allow for the inclusion of curves. Bends and curves can help you to create a stunning look and enable you to make the best use of the available space.


Drawbacks of Metal Frames for Decking

As with anything in life, there are potential downsides to metal frames:

Higher Initial Cost

Metal frames, especially those made from high-quality steel or aluminium, tend to be more expensive to purchase than wooden frames. But they are significantly longer lasting and so should be cheaper in the long run.


Most DIY enthusiasts would be comfortable working with wood but may not have worked with metal, a rigid and unforgiving material that requires the use of specific tools to cut it. However, many manufacturers of steel and aluminium decking can supply a subframe in kit form that merely requires assembly.

Aesthetic limitations

While metal frames offer a sleek and modern appearance, some homeowners may prefer the natural and traditional look of timber. It is important to remember that any visible areas of metal framing can be painted to create a more pleasing aesthetic and one that complements your property.


What is best – aluminium or steel?

If you decide that a metal frame could be an excellent solution, you need to choose between aluminium and steel.

Aluminium frames

Aluminium is significantly lighter than steel and so is easier to handle and install. This can be particularly advantageous in projects where weight is a critical factor, such as rooftop decks or structures positioned over water.

Aluminium is naturally resistant to corrosion and rust. It is, therefore, an excellent choice for environments where it is exposed to moisture, saltwater, or chemicals. Aluminium requires less ongoing maintenance than steel. It is a highly recyclable material that offers a sleek, modern look. It can be painted or coated to match other elements of your property.

You will probably find that an aluminium subframe will be more expensive than a steel construction. Aluminium is not as strong as steel and so is not the best choice for projects where a high load-bearing capacity is required. It is also worth noting that aluminium has a higher coefficient of thermal expansion than steel, meaning it can expand and contract more with temperature changes. 

Steel frames

Steel is valued for its exceptional strength and load-bearing capacity. It is ideal for large or heavily loaded decking projects where structural integrity is a primary concern.

Steel is generally more cost-effective than aluminium in terms of initial material costs, making it a more budget-friendly option for many projects. It can be easily welded, bolted, and fabricated into complex shapes, offering greater flexibility in custom designs and configurations.

But steel is much heavier than aluminium, which can complicate handling and installation. This is a significant factor in projects where ease of installation or weight limits are critical. Steel requires more maintenance than aluminium to prevent rust and corrosion. Protective coatings must be maintained and reapplied as needed to ensure longevity.

Is a metal subframe right for you?

Metal frames are superior options for most projects as they are longer lasting, more versatile and require less maintenance. They are compatible with all decking materials and will not rot, twist or bow. But the upfront costs are greater with metal frames and their modern look may not be appropriate in some settings. 

It is certainly worth exploring metal subframes before making your choice. As they can be supplied in kit form, they do not rule out DIY installation although there are certainly many benefits to engaging a professional installer.

You may not have previously considered investing in a metal subframe but there are compelling reasons to choose a steel or aluminium construction.


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