Three walls of a small addition, 44 ft of wall in all with two doors and two windows, take 63 2×4 studs at 16 in on center: 45 full-height studs, 8 jacks and 16 cripples plus 10% waste. They also need 12 plate boards of 16 ft, 8 sheets of sheathing for the two exterior walls, 4 headers and about 448 16d nails. Each header is sized from the IRC span tables for what the wall carries.
How the framing is calculated
Every wall is laid out stud by stud the way the stud calculator does it: a stud at each end and on every 16 or 24 in mark, extra studs at corners and T intersections, and a frame of king studs, jack studs, a header and cripples around each door and window. The framing calculator adds the walls up and picks a header for each opening.
Studs to buy = (full-height studs + jack studs + studs cut up for cripples) × (1 + waste). Plate boards = walls × (1 bottom + 2 top plates) × length ÷ board length, rounded up per row.
The openings are spaced evenly along each wall. Where exactly a door sits changes the count by a stud at most, so move them only if you need a precise layout.
Header sizes by opening width
The header over each opening comes from IRC Table R602.7(1) for exterior bearing walls or Table R602.7(2) for interior bearing walls, for No. 2 Douglas fir-larch, hem-fir, Southern pine or spruce-pine-fir. The calculator takes the shallowest two-ply header (three-ply in a 2×6 wall) whose span covers the rough opening. For the default house, 24 ft wide under 30 psf ground snow with the walls carrying only the roof and ceiling:
| Opening | Rough width | Header | Max span | Jacks each end |
|---|---|---|---|---|
| Entry door | 38 in | 2-2×6 | 4 ft 7 in | 1 |
| Window | 36 in | 2-2×4 | 3 ft 1 in | 1 |
| Wide window | 60 in | 2-2×8 | 5 ft 9 in | 1 |
| Partition door | 34 in | flat 2×4 | 8 ft, non-bearing | 1 |
A 2×4 laid flat is allowed over openings up to 8 ft in a non-bearing wall (IRC R602.7.4). In a bearing wall the numbers climb quickly with load: a floor above, a wider house or a heavier snow load all shorten every span. The beam span calculator shows the full table for any case.
King studs at each end come from Table R602.7.5. Where the design wind speed is up to 140 mph, a header up to 4 ft long needs 1, up to 8 ft needs 2, which is why the 60 in window gets two kings on each side. In a 115 mph, Exposure B area the counts drop to 1 up to 8 ft.
Wall framing basics the calculator follows
- Plates: a single bottom plate and a double top plate. IRC R602.3.2 asks for joints in the two top plates to be at least 24 in apart and for the top plates to overlap at corners and bearing partitions.
- Stud spacing: Table R602.3(5) allows 2×4 bearing studs at 24 in when they carry only a roof and ceiling, 16 in with a floor above; 2×6 studs may stay at 24 in with one floor.
- Corners: three studs is the standard corner. The two-stud corner with drywall clips, from advanced framing (Building Science Corporation, BSI-030), saves a stud per corner and leaves room for insulation.
- Sheathing: exterior walls get 4 × 8 ft panels run vertically, counted as whole panels per 4 ft of wall and per 8 ft of height.
Nails
The nail count follows IRC Table R602.3(1) with 16d common nails (3½ × 0.162 in): 2 end nails through the plate into each end of every stud, 3 into each end of a header, top plate to top plate every 16 in, the bottom plate into the floor every 16 in, built-up headers every 16 in along both edges, and jack studs face-nailed to the kings every 24 in. Nails for sheathing depend on the panel and its fastening table and are not included. A box of nails is sold by weight, so check the count per pound on the box you buy.
Worked through: wall 1
The 20 ft exterior wall has three-stud corners at both ends, one T intersection, a 38 × 82½ in door and a 36 × 48 in window. Its 16 in layout gives 16 studs; the two openings displace 5 of them, leaving 11. Add 4 corner studs, 2 at the T and 4 kings (one each side of both openings) for 21 full-height studs, plus 4 jacks and 6 cripples. With the cripples cut from one more stud and 10% waste, this wall alone needs 29 studs. The drawing shows the wall exactly as counted.
Next steps
- Cover the frame: the plywood calculator for sheathing and subfloor, the drywall calculator for the inside.
- Price the lumber by the board foot with the board foot calculator, or by the piece with the lumber calculator.