How to Build A Deck

Step by step instruction to build a deck

Follow the step-by-step instruction to build a deck.

What You’ll Need


  • Timber Posts (100 x 100)
  • Bearers (90 x 90)
  • Joists (90 x 45)
  • Decking Boards (range of sizes depending on look and application)
  • Concrete/Rapid Set
  • Nails (GAL)
  • Dyna bolts
  • Coach Screws
  • Decking Screws (GAL or Stainless)
  • Joist Hangers
  • Framing Anchors
  • Post Anchors
  • Decking Stain (if needed)


  • Tape measure
  • Pencil
  • Hammer
  • Power Drill w/ bits
  • Power Saw/Hand Saw
  • Spirit Level
  • String Line
  • Shovel
  • Carpenter’s Square
  • Adjustable Spanner

What to Do

Step 1: Choose and prepare your site

Start with a site inspection. For most houses, the most practical spot for a deck is along the back wall next to a door. This provides easy access to the house. Convenience isn’t the only matter to consider, factor in natural elements such as winds in your area and how the sun will hit the deck, with north facing decks to try and be avoided. Pay special attention to the location of drains and any external plumbing, because once your deck has been built, it will be hard to access the area under it.

After you have selected your preferred deck site, prepare the ground by making sure the area has adequate ventilation and drainage, you may have to lay some Agi-Pipe before you start building to avoid any surface water lying about underneath. Rake the area clear and undertake any weed control that might be necessary (weed killer or weed mat).


Step 2: Mark out the site

*This stage requires you to be very accurate, so take your time and don’t rush, it will save you a lot of time and money further down the track.

Mark out the width and length of the deck where it will connect to the house using stakes and string line. As you proceed, make sure the marked area is square, you can check this be measuring the diagonals and making sure they are equal lengths.

Figure 1: How to get a square area
Figure 1: How to get a square area


Step 3: Set out the posts

Set up the bearer spacings at a minimum of 1800mm centres with stump holes no more than 1500mm apart. The outside run of stumps will need to align with the outside edge of the deck.

If setting timber post straight into the ground you may wish to coat the timber that comes in contact with the ground with some type preservative.

If using stirrups allow for at least a 75mm clearance between the ground and the bottom of the post.

Fill the hole with a mixture of approximately 2 bags of concrete or rapid set mix following the guidelines on the bag.

Use a spirit level to make sure posts are vertical, then temporarily brace the posts and allow for concrete to set.

Figure 2: Decking Terminology
Figure 2: Decking Terminology


Step 4: Add the framing

Measure the decking, joist and bearer thickness.

Against the house wall measure this thickness down from the intended floor height of the deck.

If your house is brick then connect a 140 x 45mm F.7. timber ledger to the brickwork using dyna bolts at 450mm intervals. If you have a weatherboard house, ideally bearers should be joined to the existing bearers of your house; however you may use a timber ledger in a similar fashion as a brick house, using coach screws instead of dyna bolts.

Once the plate has been fixed and therefore the bearer height determined, the posts can be marked for cutting to height. Make sure that allowance is made for the method of fixing the bearer before determining the cutting height of the posts, then using a square, string line and level mark all the remaining posts and cut them to the correct height.

Fix remaining bearers to posts, using either a framing anchor or housing joint.

Check all levels and angles once again.

Set joists on top of bearers every 450 – 600mm for hardwood decking using framing anchors.


Step 5: Lay the decking

Beginning next to the house wall, lay decking across the joists, screwing to each joist with two stainless or galvanised screws, pre-drilling to avoid the timber splitting. Ensure this is done carefully as this is the most visible part of the deck.

Use spacers approximately 5mm thick for small boards and up to 8mm thick for larger boards to ensure a neat finish. By checking the intended finishing width of the deck minor adjustment can be made to this spacing to ensure the outside decking board finishes in the correct location. This may include allowance for any barge boards fitted to the stumps below the deck.

Make sure all decking board joins are over a joist, and these should be randomly positioned on different joists so they blend into the finished deck and are not noticed.

A string line should be run or chalk line flicked alongside every 4th or 5th board as they are being laid to check and adjust for straightness.

To get a straight, even edge to the finished deck, let the ends overhang about 50mm, then trim them all together with a circular saw when you’ve completed laying all boards.


Step 6: Finish the Deck

If you have chosen a hard durable decking surface such as spotted gum or ironbark, a decking finish is optional. Remember, most timbers left to age naturally will turn to a silver grey colour over a year or so after completion. We do advise you to use an oil or sealer to help maintain the beauty and life of your deck. Finishes come in a range of colours and types so feel free to call or come into our store to ask us on some advice or collect some free samples.