8 × 5 m deck: materials list and cost
A 8 × 5 m deck is 40 m². Built against the house, 450 mm off the ground, the materials come to about $7,880 in merbau or $11,455 in composite decking.
Merbau decking
$7,880
about $197 per m²
Composite decking
$11,455
about $286 per m²
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Materials list: merbau
| Item | Qty | Cost |
|---|---|---|
| Merbau decking boards 140 × 19 | 309 m | $3,075 |
| Merbau edge face board | 19 m | $189 |
| Joists 140 × 45 H3 treated pine, 5.4 m | 19 | $1,239 |
| Bearers 190 × 45 H3 treated pine, 4.8 m | 8 | $601 |
| Posts, with concrete and a stirrup (allowance of $100 each) | 24 | $2,400 |
| Joist hangers, screws and fixings (5%) | $375 | |
| Estimated materials total | $7,880 | |
Materials list: composite
| Item | Qty | Cost |
|---|---|---|
| Composite decking boards 137 × 23, 5.4 m | 59 | $5,796 |
| Composite edge face boards, 5.4 m | 4 | $393 |
| Hidden clip kits for composite (each covers 100 m of board) | 4 | $480 |
| Joists 140 × 45 H3 treated pine, 5.4 m | 19 | $1,239 |
| Bearers 190 × 45 H3 treated pine, 4.8 m | 8 | $601 |
| Posts, with concrete and a stirrup (allowance of $100 each) | 24 | $2,400 |
| Joist hangers, screws and fixings (5%) | $545 | |
| Estimated materials total | $11,455 | |
What this price assumes
- A plain rectangle, 8 m along the house and 5 m out from it.
- 450 mm from the ground to the top of the deck, with no stairs, balustrade or pergola.
- A treated pine frame: joists at 450 mm centres on bearers and posts, each joist cut from the shortest stock length that covers it.
- Bunnings “from” prices checked October 2026, plus 8% extra decking for offcuts. Prices vary by store and over time.
What changes the cost
- Height. A higher deck needs longer posts and more bracing. Decks more than 1 m off the ground need a balustrade.
- Stairs. Each set adds stringers and treads.
- Decking choice. Spotted gum, blackbutt and jarrah usually cost more than merbau. Treated pine decking costs less.
- Labour. These are materials only. Save your design and you can ask a local builder to quote the labour from it.
Other deck sizes
3 × 3 m4 × 3 m4 × 4 m5 × 3 m5 × 4 m5 × 5 m6 × 3 m6 × 4 m6 × 5 m6 × 6 m8 × 4 m8 × 5 mAll sizes
This is a guide only, not engineering or building advice. Spans, footings and post sizes depend on your site, height and local rules, so check your design with a builder or engineer before you buy or build.