Counting a wall
A stud wall is a bottom plate, a top plate, studs between them at a fixed spacing, and noggins across the studs to stop them twisting. Count the common studs first: the wall length divided by the spacing, rounded down, plus one for the far end. Then add the studs that do not sit on the grid, which is where most people undercount: two at every corner and T-junction so there is something to nail the lining to, and four at every door and window for the jamb studs either side and the jack studs under the lintel.
studs = (length ÷ spacing, rounded down) + 1 + 4 per opening + 2 per corner
| Wall | Common studs | Extras | Total | Plates |
|---|---|---|---|---|
| 3 m internal, 450 c/c, one door, one junction | 7 | 6 | 13 | 6.3 lm |
| 6 m external, 450 c/c, one window, two corners | 14 | 8 | 22 | 12.6 lm |
| 6 m external, 600 c/c, one window, two corners | 11 | 8 | 19 | 12.6 lm |
| 12 m garage wall, 450 c/c, roller door 3 m, two corners | 27 | 8 | 35 | 25.2 lm |
Plates are for a single top plate. Add another wall length for a double.
Spacing and size
450 mm centres is the default for Australian house framing and it suits 10 mm plasterboard, 6 mm fibre cement and every cladding on the market. 600 mm centres is permitted by AS 1684 for many walls, particularly non-loadbearing internal walls and lightly loaded single-storey walls, and it saves about a quarter of the studs, but the lining has to be rated for it (13 mm plasterboard or 10 mm with the right fixing) and loadbearing walls need to be checked against the span tables for the roof and floor load they carry. External and loadbearing walls are 90 × 45 MGP10 as a rule; internal partitions are often 70 × 35. In termite areas, which is most of Victoria, framing is either treated or protected by a termite management system.
Noggins and lintels
Noggins go in rows so that no unsupported length of stud exceeds 1,350 mm, which means one row in a 2.4 or 2.7 m wall and two in a 3 m wall. They are cut to fit between the studs, offset slightly so each one can be nailed through the stud, and they double as fixing for basins, grab rails and TV brackets if you put them where those will go. Lintels span the openings and carry whatever is above: in a non-loadbearing wall a piece of stud timber on flat is enough, in a loadbearing wall the size comes from the AS 1684 span tables for the span and the roof load, and over a big opening it may be an LVL or steel from the engineer.
Worked example
A 6 m external wall, 2.4 m high, 90 × 45 at 450 centres with a single top plate, one 1.2 m window and two corners. Common studs 6 ÷ 0.45 = 13.3, so 13 plus one, 14. Add four for the window and four for the corners: 22 studs at 2.31 m, bought as 2.4 m. Plates 12.6 lm, one row of noggins 6.3 lm, and a lintel 1.4 m long sized from the tables. About 71 lineal metres of stud-size timber, plus the lintel.
Common questions
How many studs for a wall?
Length ÷ spacing rounded down, plus one, plus four per opening and two per corner.
450 or 600 centres?
450 is the safe default. 600 is allowed for many walls under AS 1684 if the lining suits and the loads check out.
Stud length for a 2.4 m wall?
2,310 mm with a single top plate in 90 × 45, cut from 2.4 m stock.
How many noggin rows?
One up to 2.7 m, two at 3 m, keeping gaps under 1,350 mm.
Quantities only. Stud spacing for loadbearing walls, lintel sizes, bracing and tie-downs come from AS 1684 or the engineer's design for the house.