How do you build a deck in Australia?
Work through five things in order: approvals, footings, bearers, joists, then boards. Skipping ahead is how decks end up out of level or fail an inspection. This guide follows WoodSolutions’ Technical Design Guide 21 for timber decks, which bases its framing on AS 1684, and adds what builders say on video.
Do you need approval to build a deck?
Often not for a small, low deck, and the thresholds differ by state and council, so check yours first.
| Where | What we found |
|---|---|
| NSW | Exempt if 25 m² or less, floor no more than 1 m above existing ground, 3 m or less overall, at least 900 mm from the boundary (5 m in some rural zones), behind the building line. On bushfire-prone land within 5 m of the house, the deck must be non-combustible |
| Queensland | Building approval if the plan area is over 10 m², overall height is over 2.4 m, a side is over 5 m, the floor is over 1 m above ground, or the deck isn’t freestanding. Brisbane City Council’s no-approval test is 10 m², 1 m and no roof |
| South Australia | Marion Council says no approval if no part is more than 500 mm above ground and none is within 900 mm of the boundary |
| Victoria | A Victorian council says a building permit may be needed if the deck is attached to or within 900 mm of a building, larger than 10 m², at the front, or attached to a pool; another says a building permit is always needed. Planning permits depend on zone, lot size and height |
| Western Australia | A Perth council requires a permit over 20 m², above 500 mm, within 900 mm of a boundary, in a bushfire prone area or with privacy screens |
These come from state fact sheets and council pages, not one authority, and the Victorian and South Australian state sites weren’t readable. Ask your council before you buy anything.
What size posts and bearers do you need?
The sizes come from AS 1684 tables, not from a rule of thumb. WoodSolutions points to Table 49 for bearers and Table 50 for joists when the deck floor is more than 1,000 mm above ground, and Tables 5 and 6 when it is 1,000 mm or less. Those tables apply to decks with timber boards only; tiled decks and spas need an engineer.
Posts follow a height rule: the maximum height of a deck above ground is 15 times the post’s face width, and posts must be braced to AS 1684. The joists and bearers guide explains how the pieces fit together.
How far apart do the joists go?
It depends on the board. For timber boards WoodSolutions’ Table 2 gives these maximum joist spacings:
| Board | Maximum joist spacing |
|---|---|
| Hardwood, 19 mm | 500 mm |
| Cypress, 19 mm | 400 mm |
| Cypress, 21 mm | 450 mm |
| Treated softwood, 19 mm | 400 mm |
| Treated softwood, 22 mm | 450 mm |
Boards laid at an angle need closer joists. WoodSolutions’ example: 19 mm standard grade hardwood boards at 45 degrees need joists at 350 mm to keep the allowable 500 mm board span. For composite, use the maker’s spacing; see installing composite decking.
How do you attach a deck to a house?
With a waling plate, within limits. WoodSolutions’ deemed-to-satisfy method applies only to decks no more than 3.0 m above the top of footings, not cantilevered, with a live load of 2 kPa or less, on a timber-framed external wall to AS 1684. The waling plate is at least 190 by 45 mm, MGP10 or F5 or better, fixed at 300 mm centres or less with M12 coach screws or bolts. Otherwise build a free-standing structure or use an engineer.
Where cladding is removed for the attachment, flashing must be provided to stop moisture entering the house. Brace the deck with 30 by 0.8 mm steel strap at 30 to 60 degrees to the waling plate where the surface is 1 m or more above the ground.
What fixings and protection should you use?
Hot-dipped galvanised or stainless steel, never electroplated, and stainless within 1.0 m of a pool edge or 1 km of the coast. A 110 mm malthoid damp-proof strip or a proprietary strip on top of the joists adds service life. Joists should be at least 45 mm wide in seasoned hardwood or treated softwood, or 50 mm in unseasoned hardwood.
If your frame is steel, WoodSolutions says ordinary timber-deck screws aren’t suitable because differential expansion can shear them. Fix a timber batten above or beside the steel joist and screw the boards into that.
What do builders say about the order of work?
An Australian treated pine supplier’s video begins with the layout: string lines, with spray paint where they cross to mark stump positions. It sets the deck height by running a level from the existing floor or brickwork and notching the bearer to suit, fixes the wall plate to the house, then hangs the first joist before filling in the rest. For the boards, lay the first one, use a spacer for the rest, and adjust the spacing slightly so the last board finishes in the right place. Decide on stairs early, and whether the deck sits level with the indoor floor.
Another builder, working over uneven concrete, built and levelled the perimeter first and filled the middle after. A third says to sight down each joist and turn any bow so it faces up, and to join bearers directly over a post.
Do you need a railing or balustrade?
If a fall of 1 m or more is possible, yes. The NCC 2022 Housing Provisions require a barrier at least 1 m high on a deck, with no opening that lets a 125 mm sphere through. Where a fall of more than 4 m is possible, horizontal elements between 150 and 760 mm above the floor must not make the barrier climbable. Stairs have their own limits; see deck stairs.
Can you frame a deck in aluminium instead?
Yes, over a slab or on pedestals, with the maker’s own span tables. See aluminium deck frames and steel against aluminium.
Aluminium frame estimator
Preliminary · not engineering- Deck area20 m²
- Supports per joist—
- Supports in total—
Support (pedestal or footing) spacing depends on the frame system, load and height. Take it from the frame manufacturer’s span table or an engineer; we do not estimate it.
This is a preliminary materials count, not an engineering design. It does not confirm spans, load capacity or code compliance.
Questions
How do I build a deck on the ground?
Keep the frame clear of the soil: Ekodeck wants 40 mm of ground clearance with drainage and 90 mm without, and Futurewood 100 mm. Boards more than 400 mm above the ground count as a raised deck in WoodSolutions' terms, and then you need drainage and cross-flow ventilation underneath.
Can I build a deck myself in Australia?
Yes, for a light domestic deck, as long as the council rules and the standards are followed. WoodSolutions' guide covers light domestic decks and says anything heavier, such as tiled floors, spas or vehicles, needs a structural engineer.
Do I need a deck builder?
Not always. Hire one if the deck is high, attached to the house in a way you can't do to the standard, tiled or carrying a spa, or if you want the work signed off. Ask which standard or maker's guide they build to, and who handles the approval.
What is the difference between DIY decking and a deck kit?
A kit supplies a pre-sized frame and fixings for a set area, whereas DIY decking means you buy and cut the timber yourself to the AS 1684 tables. Check what spans and loads a kit assumes before you buy it.
Do I need a railing on my deck?
Under the NCC 2022 Housing Provisions, a barrier is needed wherever it is possible to fall 1 m or more. The barrier has to be at least 1 m high on a deck and its openings must stop a 125 mm sphere. Aluminium and glass systems are fine, but they have to meet the same rules.
Sources
- WoodSolutions TDG 21 Domestic Timber Deck Design (revised Oct 2020)
- NSW Planning: Balconies, decks and patios
- Queensland: Decks and covered areas
- Brisbane City Council: Building a deck
- Boroondara: Deck permits
- City of Joondalup: Decks
- What needs Development Approval - Marion Council fact sheet (July 2026)
- Decks - Do I Need a Building Permit - Monash City Council
- Ekodeck Classic Decking | Tech Specs | Composite Decking
- Fixing Guidelines - Futurewood
- Part 11.3 Barriers and handrails - NCC 2022 Housing Provisions (ABCB)
- Installer video: How To Build A Deck in Australia - Step by Step Guide (Australian Treated Pine)
- Installer video: How To Install Picture Frame Composite Decking / Steps / on Concrete Slab / Frontyard / DIY (A Perspective)
- Installer video: How To Build A Deck Part 3: Bearers and Joists (Handyman Magazine)