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When building a deck, understanding its structural components is essential. From posts and bearers to decking boards and noggings, each element plays a key role in supporting the deck.
This simple guide explains the function of decking components and how they work together to create a safe and secure deck that is durable.
We also recommending reading the comprehensive step-by-step How to build a deck series by the Bunnings team - an invaluable resource for anyone starting a new deck build.
Posts or pedestals
Posts or pedestals are vertical components that provide foundational support for your deck, transferring its weight to the ground or a solid foundation. Made from treated timber, concrete or metal, posts are either embedded in the ground (for ground-level decks) or sit on footings (for elevated decks). Posts must be sized to handle the load from the bearers and additional weight like furniture or people. Proper anchoring is essential to prevent shifting, especially in unstable soil or flood-prone areas.
Bearers
Bearers are horizontal supports that sit on top of the posts, distributing the load from the joists and decking boards down into the posts. They are typically larger than joists and must be sized to carry the deck’s weight and any additional loads. Bearers are usually made from treated timber, engineered wood, or steel. Common sizes include 140mm x 45mm, 190mm x 45mm, and 240mm x 45mm, depending on the span between posts. Proper spacing and secure attachment to posts are both critical to prevent sagging or deflection.
Joists
Joists run perpendicular to the bearers, forming the framework that supports the decking boards. They are spaced at intervals (typically 400mm to 450mm apart) to support the decking material and prevent deflection. Joists distribute the deck's weight to the bearers and provide stability. Joists are typically made from treated timber or engineered wood products like Laminated Veneer Lumber (LVL). Their size and spacing depend on the decking material and load requirements.
Decking boards
Decking boards form the surface layer of the deck and sit on top of the joists. Made from timber or composite material, decking boards are typically spaced 5mm to 6mm apart to allow for drainage and airflow. This gap helps prevent moisture buildup, which can lead to rot in timber decks. Decking boards are laid perpendicular or at a 45-degree angle to the joists.
Noggings
Noggings are small timber blocks installed between joists to prevent twisting and add stability. Although they don’t directly support load, they help maintain the alignment of the joists and keep the deck frame square and rigid. Noggings are usually placed at regular intervals to prevent warping, especially in decks with wide spans.
More help for building your deck
A well-built deck adds value to your outdoor living space and your home. Understanding the roles of posts, bearers, joists, decking boards, and noggings is essential when designing your new deck. Each component contributes to the deck’s stability, safety and overall performance.
Always consult with professionals, use the correct materials, and refer to span tables to ensure components are appropriately sized and spaced. If you need assistance with your deck build, feel free to Ask a question and our community members will be happy to help.
