Decking Joists: Why Aluminium Sub-Frames Are the Future of Decking

Decking is a great way to enhance the outdoor living space of your home. It provides an additional area to entertain guests, relax, and enjoy the fresh air. However, constructing a deck involves several components, one of which is decking joists. 

You might be wondering, “What are aluminium deck joists?” And most importantly, why are aluminium sub-frames becoming the future of decking? 

What Are Decking Joists?

Decking joists are an essential component in any decking project, providing the structural support necessary to create a stable and long-lasting deck. These horizontal beams, typically made of wood, steel, or aluminium, are placed parallel to each other and perpendicular to the deck boards.

The primary purpose of decking joists is to evenly distribute the weight and load of the deck, ensuring it remains structurally sound and capable of supporting the weight of people, furniture, and other items. They serve as the framework upon which the deck boards are installed, providing a stable surface for walking and relaxing.

Proper spacing and levelling of joists are crucial for the integrity of the deck. The spacing between joists determines the stability and strength of the deck, preventing sagging or bouncing when weight is applied. It is important to follow manufacturer guidelines or consult with a professional to determine the appropriate spacing based on the materials used and the intended purpose of the deck.

Levelling the joists is equally important to create a flat and even surface for the deck boards. Uneven joists can lead to an uneven deck surface, compromising not only the aesthetic appeal but also the safety and stability of the deck.

When it comes to the types of decking joists available, the most commonly used material is wood. Wood joists are readily available, relatively inexpensive, and can be easily cut and shaped to fit specific project requirements. However, they are prone to issues such as rotting, warping, and pest infestation, which can compromise the longevity and structural integrity of the deck.

In recent years, alternatives to traditional wood joists have gained popularity, including steel and aluminium. Steel joists offer increased strength and durability, making them suitable for decks that require longer spans or have heavy loads. However, steel joists can be heavier, more expensive, and may require additional protective coatings to prevent rust and corrosion.

Aluminium joists have emerged as a promising alternative to both wood and steel. They are lightweight yet exceptionally strong, making them easier to handle and install. Aluminium is resistant to rot, warping, and pests, ensuring a longer lifespan for the decking structure. Additionally, aluminium joists are often made from recycled materials, making them an eco-friendly choice.

Problems with Traditional Wood Joists

Traditional wood joists have long been a popular choice due to their availability and familiarity. However, they come with a range of common issues that can significantly impact the lifespan and performance of a decking project. Understanding these problems is crucial in recognizing why aluminium sub-frames are emerging as the future of decking joists.

One of the primary challenges with traditional wood joists is their susceptibility to rotting and warping. Wood is a natural material that is prone to decay when exposed to moisture, especially in outdoor environments. Over time, water can penetrate the wood fibres, leading to rot and structural instability. Additionally, fluctuations in temperature and humidity can cause wood joists to warp, resulting in an uneven and unstable decking surface.

Another limitation of wood joists is their maintenance requirements. Wood requires regular sealing, staining, and treating to protect against moisture damage and to maintain its structural integrity. This maintenance can be time-consuming and costly, as it needs to be done periodically to preserve the wood’s appearance and prevent deterioration. Failure to properly maintain wood joists can accelerate their deterioration, leading to shorter lifespans and the need for premature replacements.

Fortunately, these issues can be effectively addressed by using aluminium sub-frames for decking projects. Aluminium is a highly durable and weather-resistant material that is inherently resistant to rot, warping, and corrosion. Unlike wood, aluminium does not absorb moisture, making it impervious to rot. It remains stable and retains its structural integrity even in harsh weather conditions, ensuring a longer lifespan for the decking structure.

Moreover, aluminium sub-frames offer significant advantages in terms of maintenance requirements. Unlike wood, they do not require regular sealing, staining, or treatment to protect against moisture damage. Aluminium’s natural resistance to corrosion and decay eliminates the need for ongoing maintenance, saving both time and money in the long run. This low-maintenance characteristic makes aluminium sub-frames an attractive option for homeowners and contractors alike.

Benefits of Using Aluminium Sub-Frames for Decking 

Aluminium sub-frames have gained significant popularity in the world of decking due to their numerous advantages over traditional wood joists. These innovative structures effectively address the problems commonly associated with wood joists while offering unmatched longevity, durability, low-maintenance requirements, and eco-friendly characteristics. 

  1. Addressing the Problems of Wood Joists: One of the major drawbacks of traditional wood joists is their susceptibility to rotting, warping, and decay caused by exposure to moisture, insects, and the elements. Aluminium sub-frames provide a superior alternative by being highly resistant to these issues. Aluminium does not rot, warp, or degrade over time, ensuring a stable and long-lasting foundation for your decking. This inherent resistance makes aluminium sub-frames ideal for outdoor environments where moisture and weather elements can take a toll on wood joists.
  2. Longevity and Durability: When it comes to durability, aluminium sub-frames outshine wood joists by a considerable margin. Aluminium is a robust material known for its exceptional strength-to-weight ratio and resistance to corrosion. It can withstand heavy loads and foot traffic without compromising its structural integrity. This durability translates into a longer lifespan for your decking, reducing the need for frequent replacements or repairs that are often required with wood joists. With aluminium sub-frames, you can enjoy a sturdy and long-lasting deck for many years to come.
  3. Low-Maintenance Nature: Maintaining a deck can be a time-consuming and labour-intensive task, particularly when it involves the upkeep of wood joists. Wood requires regular sealing, staining, and painting to protect it from moisture and prevent decay. In contrast, aluminium sub-frames are virtually maintenance-free. They do not require staining, sealing, or any protective treatments. A simple periodic cleaning with mild soap and water is usually sufficient to keep them in optimal condition. This low-maintenance feature of aluminium sub-frames not only saves you time and effort but also eliminates the ongoing costs associated with maintaining wood joists.
  4. Eco-Friendly Choice: In an era where sustainability is a growing concern, choosing eco-friendly materials for construction projects is becoming increasingly important. Aluminium sub-frames offer an environmentally conscious option for decking. Aluminium is a highly recyclable material that can be reused without compromising its quality. By opting for aluminium sub-frames, you contribute to the reduction of deforestation and the demand for new wood products, ultimately helping to preserve forests and conserve natural resources.

Cost Comparison 

Cost is an essential factor to consider when it comes to selecting the right decking joists for your project. Traditional wood joists have been a popular choice for many years due to their affordability. But, it’s crucial to evaluate the long-term investment and savings that come with choosing aluminium sub-frames.

At first glance, traditional wood joists may appear to be the more cost-effective option. They are readily available and typically have a lower upfront cost compared to aluminium sub-frames. However, it’s essential to look beyond the initial expense and consider the long-term benefits that aluminium sub-frames offer.

Let’s consider the initial investment of aluminium sub-frames. While they may have a higher upfront cost compared to wood joists, they provide exceptional value for money. Aluminium sub-frames are known for their durability and longevity, significantly outperforming traditional wood joists. They are highly resistant to rotting, warping, and insect damage, ensuring that your deck will maintain its structural integrity for many years to come.

Furthermore, aluminium sub-frames require minimal maintenance compared to wood joists. Wood joists often need regular treatments, sealants, and inspections to prevent rot and decay. On the other hand, aluminium sub-frames are virtually maintenance-free, saving you both time and money in the long run. Additionally, the reduced maintenance costs associated with aluminium sub-frames contribute to their overall cost-effectiveness.

In terms of durability, aluminium sub-frames are unmatched. They can withstand various weather conditions, including heavy rain, extreme heat, and freezing temperatures, without warping or deteriorating. This durability ensures that your deck remains stable and safe for years, reducing the need for costly repairs or replacements.

While the initial investment for aluminium sub-frames may be higher, the long-term savings and benefits they offer outweigh the costs. Their durability and reduced maintenance requirements mean you’ll save money on repairs and replacements in the future. Additionally, their long lifespan adds value to your property and can even increase its resale value.


If you’re planning a decking project, consider using aluminium sub-frames. They offer various benefits that make them a cost-effective, durable, and eco-friendly choice. With little to no maintenance required and a long lifespan, they are quickly becoming the future of decking.