450 or 600 centres — what actually decides it
Every second tradie has a default in their head, and both defaults are right some of the time. The spacing isn't a preference. In Australian light timber framing it falls out of the AS 1684 span tables, and those tables are read against four things about your wall:
- Wind classification — N1 through N6 for non-cyclonic areas, C1 through C4 in cyclone country, assessed under AS 4055. A coastal N3 site loads a wall harder than a sheltered N1 one, and the table answers differently.
- Roof load width — how much roof each metre of wall is carrying. A wall under a wide truss span with a tiled roof is a different member to the same wall under a sheet roof.
- Stud size, grade and species — 90 × 45 MGP10 doesn't span what 90 × 45 MGP12 spans, and unseasoned hardwood is a third set of numbers again.
- Wall height and storey — a 2.4m single-storey wall and a 2.7m ground-floor wall carrying a second storey are not the same problem.
What that means in practice: 600 centres in 90 × 45 is common for a single-storey external wall in a low wind area, and 450 turns up as soon as the loads climb, the wall gets taller, or you're using a smaller section. Get the spacing off the span table, the frame drawing or the engineer — then put it in the box above and let this count the sticks.
A worked example
A 4.8m external wall, 2.4m high, framed at 600 centres, with one window and two corners:
- Common studs: 4800 ÷ 600 = 8 bays, so 9 studs
- Extras: 1 window × 2 jamb studs + 2 corners × 2 = 6 studs
- Total studs: 15 at 2.4m = 36.0 lineal metres
- Plates: 3 × 4.8 = 14.4 lineal metres
- Noggins: one row × 4.8 = 4.8 lineal metres
- Total: 55.2 m, plus 5% waste = 58.0 lineal metres
The same wall at 450 centres: 11 bays, 12 common studs, 18 studs all up and 65.5 lineal metres. Three extra studs and about seven metres more timber — a small difference on one wall, a real one across a house.
Common Australian framing sections
| Section | Typically used for |
|---|---|
| 70 × 35 | Non-loadbearing internal walls, bulkheads, furring |
| 90 × 35 | Internal walls, light loadbearing work at closer centres |
| 90 × 45 | The workhorse — external walls and loadbearing internal walls |
| 140 × 45 | Taller walls, heavier loads, walls housing services or extra insulation |
Sizes are the finished seasoned dimensions. Grade matters as much as size — MGP10, MGP12 and F17 hardwood all read off different lines of the table.
Plates, and why three
The default here is three plates: one bottom plate and a double top plate. A double top plate is the normal detail on a loadbearing wall where roof or floor loads don't land directly over a stud. Plenty of non-loadbearing internal walls run a single top plate — set the plate count to 2 and the numbers follow. Which one your wall needs is an AS 1684 question, not a habit.
Noggins
Noggins stop the studs twisting, stiffen the wall, and give you something to screw plasterboard, a towel rail or a TV bracket to. One row per 1350mm of height, less one, is the rule this calculator uses:
| Wall height | Noggin rows |
|---|---|
| 2.4 m | 1 |
| 2.55 m | 1 |
| 2.7 m | 1 |
| 3.0 m | 2 |
| 3.6 m | 2 |
Plasterboard comes 1200mm wide. If you're sheeting horizontally, put the noggin row where the sheet joint lands rather than at dead centre — you'll thank yourself at stopping time. Add extra noggins wherever a vanity, a grab rail or a wall-hung toilet is going, while the wall is still open.
What this count leaves out
Two studs per opening is the jamb studs only. A real opening also needs a lintel sized for the span and the load, jack studs under it, and cripple studs above the lintel and below the sill. Corners need a nogged corner post or a stud-and-block detail so the plasterboard has an edge to land on both sides. Add those off the frame drawing — this gives you the base count to start from, not the cutting list.
Frame counted. Now price the job.
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Try Yamate free → Free to try · no card · sign in with a link, no password to rememberWall framing & stud spacing FAQ
Should studs be at 450 or 600 centres in Australia?
It depends on wind classification, roof load width, stud size and grade, and wall height — all read off the AS 1684 span tables. 600 centres is common for a single-storey external wall in 90 × 45 in a low wind area; 450 turns up as loads or heights increase. Take it off the span table or the frame drawing.
How many studs do I need for a 6 metre wall?
At 600 centres, 10 bays and 11 common studs. At 450 centres, 14 bays and 15 common studs. Then add two studs per door or window and two per corner.
Why is it studs plus one?
Because studs sit at both ends of every bay. A 3600mm wall at 600 centres has 6 bays but 7 studs — the fencepost problem. Miss it and you're one stud short on every wall in the house.
How many plates does a stud wall have?
Usually three — one bottom plate and a double top plate on a loadbearing wall. Non-loadbearing internal walls often run a single top plate, making two. AS 1684 sets which detail your wall needs.
How high should noggins be?
One row near mid-height for a standard 2.4m wall, two rows once the wall gets past about 2.7m. If you're sheeting plasterboard horizontally, line the row up with the 1200mm sheet joint so the edge is supported.
Does this calculator tell me what size studs to use?
No, and no free calculator honestly can. Member size and spacing come from the AS 1684 span tables against your wind classification, roof load width, species and grade. This counts members at a spacing you supply.
Other calculators you'll want
General information for Australian trades, and an estimate only — not tax, financial or legal advice. It is not engineering, building or design advice either: a calculator works out a quantity from the figures you enter, and anything that needs sign-off still needs your engineer, certifier or building surveyor. This tool counts framing members at the spacing you enter. It does not select stud spacing, member sizes, lintels or bracing — those come from AS 1684, your wind classification under AS 4055, and your frame drawing or engineer. Standards are published and sold by Standards Australia and are not reproduced here. Confirm anything structural with your certifier, building surveyor or engineer.