Columns: Stud Packs

Last updated April 20, 2023
By Ian Story

The following table applies to stud packs – bundles of studs within a wall assembly that are not fastened together sufficiently to meet the NDS specifications for Built-Up Columns (NDS 15.3). As such, the studs in the pack do not reliably generate composite action, so each is assumed to carry load on its own.

Let us further assume that sheathing nailing is only nailed to one of the studs. The other studs are nailed to each other, but not well enough to reliably provide restraint for weak axis bracing. I am comfortable assuming that the second stud is restrained by the first, but I am not comfortable making that assumption for additional studs. Any additional studs are assumed to be unbraced, so will buckle at a much lower axial load. Once a column has buckled, it will continue supporting a force equal to its buckling load, but has zero stiffness to support any additional load. Therefore, the contribution of any additional studs to the overall axial capacity will be small. These additional studs do, however, help spread out load at the base and can help reduce the bearing stress at the plates. Additionally, the extra studs also contribute to bending strength, which reduces the impact of eccentric loading and bending moments.

The following table assumes live loads.

Assumes pinned-pinned column

Assumes all load applied at the top

Assumes SPF stud grade

Assumes 16″ o/c stud spacing (for wind)

Assumes a ratio between dead and live loads (15 DL to 40 LL) for purposes of wind calc

Assumes 0.6W = 9.6 psf

2×4 studs (Exterior Wall w/ wind load)

Height	(1) 2×4	(2) 2×4	(3) 2×4	(4) 2×4
6.0 ft	1,418	2,836	3,384	3,932
6.5 ft	1,342	2,684	3,169	3,654
7.0 ft	1,266	2,533	2,964	3,395
7.5 ft	1,192	2,385	2,771	3,157
8.0 ft	1,121	2,242	2,589	2,936
8.5 ft	1,053	2,107	2,420	2,734
9.0 ft	989	1,979	2,263	2,548
9.5 ft	884	1,859	2,118	2,377
10.0 ft	758	1,747	1,984	2,221
10.5 ft	647	1,642	1,860	2,078
11.0 ft	547	1,546	1,746	1,947
11.5 ft	458	1,456	1,641	1,827
12.0 ft	378	1,328	1,544	1,716
12.5 ft	306	1,188	1,455	1,615
13.0 ft	240	1,063	1,373	1,522
13.5 ft	179	950	1,297	1,436
14.0 ft	122	847	1,197	1,356
14.5 ft	68	754	1,091	1,283

2×4 Interior Studs

Height	(1) 2×4	(2) 2×4	(3) 2×4	(4) 2×4
6.0 ft
6.5 ft
7.0 ft
7.5 ft
8.0 ft
8.5 ft	1,053	2,107	2,420	2,734
9.0 ft	989	1,979
9.5 ft	929	1,859
10.0 ft	873	1,747
10.5 ft	821	1,642
11.0 ft		1,546
11.5 ft		1,456
12.0 ft		1,373	1,544
12.5 ft			1,455
13.0 ft			1,373
13.5 ft			1,297
14.0 ft			1,226
14.5 ft			1,161	1,283