How to Build a Deck in Australia: Step-by-Step Guide for Homeowners

Let’s Break Down the Process into Manageable Steps

Building a deck might seem overwhelming, but when broken down into clear stages, it becomes an achievable project for any experienced DIYer or builder. Below is a detailed explanation of how to build a deck in Australia, step by step.

Step 1: Mark Out Your Deck Area

Before any digging or building, you need to define your workspace.

• Use stakes and string lines to clearly outline the shape and boundaries of your deck.

• Mark the corners, and use a builder’s square to ensure right angles if your design is rectangular.

• Measure diagonals to check that the structure is square.

• Consider marking the locations of posts or stumps if your deck is raised.

💡 Pro Tip: Use spray paint to mark the ground. This is especially helpful on grass or uneven surfaces and helps when digging post holes later.

Step 2: Install Footings and Stumps

This is the foundation of your deck and must be done properly to ensure safety and longevity.

• Excavate post holes according to your local building code (typically 300–450mm in diameter and at least 600mm deep).

• Pour in concrete to create solid footings. While the concrete is still wet, set your post anchors or steel stirrups into place.

• Ensure all footings are aligned and at the correct height using a laser level or string line.

• Let the concrete cure for at least 24–48 hours before proceeding.

💡 Note: In areas with high wind or bushfire risks, deeper footings and reinforced stirrups may be required. Always consult your engineer or certifier.

Step 3: Build the Frame

This is the structural skeleton of your deck and determines its overall strength.

• Use H3 or H4 treated pine, or hardwood bearers and joists suitable for outdoor use and compliant with Australian standards.

• Secure bearers to the post stirrups, then fix joists perpendicular to the bearers using galvanised joist hangers, nails, or decking screws.

• Ensure the joists are evenly spaced—typically 450mm centres for timber decking and 300mm for composite decking.

• Use a spirit level frequently to maintain levelness across the frame, especially on sloped ground.

💡 Pro Tip: Add a weed mat or gravel underneath the deck to prevent weed growth and improve drainage.

Step 4: Lay the Decking Boards

Now comes the exciting part—seeing your deck take shape.

• Start laying boards from the edge closest to the house to ensure a straight, clean starting line.

• Maintain consistent spacing (5–6mm) between boards using plastic spacers. This allows for natural expansion and contraction due to weather.

• For composite decking, use manufacturer-recommended hidden fasteners or clips for a seamless finish.

• For timber, pre-drill screw holes to avoid splitting and use stainless steel or galvanised screws to prevent rust.

💡 Safety Tip: Always wear safety glasses and gloves when cutting or screwing boards.

Step 5: Add Finishing Touches

Your deck is nearly complete, but a few final steps make a big difference in appearance and safety.

• Attach fascia boards to cover the exposed edges of the frame for a polished look.

• If your deck is raised, install stairs and ensure they meet local code in terms of tread and riser dimensions.

• Add handrails or balustrades if the deck is more than 1 metre above ground. Choose styles and materials that match your overall aesthetic.

• Sand any sharp corners or splinters, especially if you’re using timber decking.

• Apply timber oil, stain, or sealer to protect against UV, moisture, and insects (skip this step if you’re using composite decking).

💡 Maintenance Tip: Allow freshly oiled decks to dry for at least 24 hours before walking on them or placing furniture.

These steps form the essential framework of how to build a deck in Australia, ensuring not just structural soundness but also long-term performance and visual appeal. Proper planning and execution at each stage will reward you with an outdoor space that you and your family can enjoy for years to come.