What 'on-center' spacing means
Stud spacing is measured 'on-center' (o.c.) — the distance from the centerline of one stud to the centerline of the next — rather than the clear gap between adjacent studs' edges. This convention exists because sheathing, drywall and other sheet materials are attached with their edges landing on the centerline of a stud, so on-center spacing directly determines where panel edges must fall for a proper fastening pattern.
In metric framing practice, 400 mm and 600 mm on-center are the two spacings commonly used, corresponding closely to the 16-inch and 24-inch on-center spacings used in imperial (US customary) framing — 16 inches equals 406.4 mm and 24 inches equals 609.6 mm, so the metric and imperial conventions are treated as practically equivalent in everyday framing discussion even though they are not exactly identical numbers.
The material-versus-stiffness trade-off
Closer stud spacing (400 mm / 16 in o.c.) uses more studs for the same wall length, increasing lumber cost and labor for cutting and setting studs, but it also increases the wall's stiffness and load-carrying capacity, distributes concentrated loads over more framing members, and provides more solid backing for attaching fixtures, cabinets and thinner sheet materials. This is why 400 mm / 16 in o.c. is the common default for load-bearing walls in residential construction.
Wider spacing (600 mm / 24 in o.c.) uses fewer studs, reducing material and labor cost, but the wall carries less load capacity and provides less frequent backing, so it is more commonly used for non-load-bearing partition walls. Wider spacing also constrains the sheathing or drywall panel choice, since a panel must be rated to span the gap between framing members without excessive deflection — thinner panels are more often specified at 400 mm than at 600 mm spacing for this reason.
Counting studs for a wall
A simple residential material take-off starts from a base stud count: the wall length divided by the spacing, rounded up to a whole number, plus one additional stud to close out the run (since a stud is needed at both ends of the wall, not only at each interior spacing interval). This base count applies to a straight, uninterrupted wall section before any openings are considered.
Each door or window opening adds extra framing beyond the base spacing pattern: king studs (full-height studs on either side of the opening) and jack studs (shorter studs supporting the header) are conventionally estimated at 2 extra studs per opening in a simplified residential take-off. This is a simplification — the true extra framing at a given opening also depends on header size, sill framing under a window, and cripple studs above and below the header, which a detailed framing plan accounts for on a large or structurally significant opening.
Counting plates and openings
Standard residential wall framing uses a bottom plate plus a double top plate — three horizontal plate rows in total — typically supplied in 2.4 m lengths and calculated per row: plates = 2 × ⌈wall length ÷ 2.4 m⌉ (for the double top plate) + 1 more run of 2.4 m lengths (for the single bottom plate). The double top plate is standard practice because it laps at corners and intersections, tying the wall framing together and providing a consistent bearing surface for whatever is framed above.
Openings also affect plate cutting — the bottom plate is cut out at a door opening once the wall is framed and raised, and headers span the top of each opening — but the plate quantity formula above estimates total linear plate stock needed before these cuts, since the cut-out material is generally not reusable elsewhere in the same wall.
Worked example: a 6 m wall with one opening
Consider a 6 m wall with one door opening, compared at both spacing conventions. At 400 mm centers, the base stud count is ⌈6,000 ÷ 400⌉ + 1 = 16, plus 2 studs for the opening, giving 18 studs total. At 600 mm centers, the base count is ⌈6,000 ÷ 600⌉ + 1 = 11, plus 2 studs for the opening, giving 13 studs total — five fewer studs for the same wall length and opening count.
Plate quantity does not depend on spacing: for a 6 m wall, plates = 2 × ⌈6 ÷ 2.4⌉ + 1 = 2 × 3 + 1 = 7 lengths of 2.4 m plate stock, the same regardless of whether the wall is framed at 400 mm or 600 mm centers, since plate quantity depends on wall length rather than stud spacing.
| Spacing | Base studs | Studs with 1 opening | Plates (2.4 m lengths) |
|---|---|---|---|
| 400 mm (≈16 in o.c.) | ⌈6,000 ÷ 400⌉ + 1 = 16 | 16 + 2 = 18 | 7 |
| 600 mm (≈24 in o.c.) | ⌈6,000 ÷ 600⌉ + 1 = 11 | 11 + 2 = 13 | 7 |
Structural caveats
This is a material take-off estimate for a straight, simple wall — it does not size lumber (species, grade, cross-section or spacing) for a specific load case. Stud size, grade and spacing needed to safely carry a wall's actual loads, including any load-bearing role in the overall structure, snow or wind loading transferred through the roof, and any shear-wall requirement, is a structural determination governed by the applicable local building code and, for load-bearing walls or unusual conditions, should be confirmed with a qualified structural engineer or building inspector.
The 2-studs-per-opening allowance used above is a simplified estimating convention, not a structural specification: a large opening with a heavy header, a wide span, or a shear-wall requirement typically needs additional king studs, jack studs, cripple studs or blocking beyond this basic allowance, and the header itself must be sized separately according to the load it carries and the applicable span table or engineering design.
Pertanyaan yang sering diajukan
What is the difference between 400 mm and 600 mm stud spacing?
400 mm centers (roughly equivalent to 16-inch on-center imperial framing) is a common default for load-bearing walls and thinner sheet materials, offering more stiffness and backing at the cost of more lumber. 600 mm centers (roughly 24-inch on-center) uses fewer studs and is more common for non-load-bearing partitions, subject to the sheathing or drywall panel's allowable span and local building code limits.
How many studs do I need for a wall?
Count one stud per spacing interval (400 mm or 600 mm) plus one to close the run, then add 2 extra studs per door or window opening for a simplified king-and-jack-stud allowance. A 6 m wall at 400 mm centers with one opening needs about 18 studs; the same wall at 600 mm centers needs about 13.
How much extra framing does a door or window opening need?
A simplified residential estimate uses 2 extra studs (king and jack studs) per opening. Large openings with heavy headers may need additional framing — cripple studs, extra jack studs or blocking — beyond this basic allowance, which a detailed framing plan or engineer would specify.
How many top and bottom plates does a stud wall need?
Standard residential framing uses one bottom plate and a double top plate — three plate rows in total — typically supplied in 2.4 m lengths and calculated per row. Plate quantity depends on wall length only, not on stud spacing.
Do I need an engineer to choose stud spacing?
This comparison is a material take-off only. For load-bearing walls, or any wall carrying structural loads, the stud size, grade and spacing must follow the applicable local building code and, for unusual spans or loads, should be confirmed by a qualified structural engineer or building inspector.
Referensi
- American Wood Council (AWC) — Wood Frame Construction Manual: standard stud spacing conventions (16 in. / 24 in. on-center) and plate configuration for residential framing.
- International Code Council (ICC) — International Residential Code (IRC), wall framing provisions governing stud spacing, size and load-bearing requirements.
- Standard residential framing trade convention for king/jack stud allowance around door and window openings.