Southern Pine, Select Structural - Design Values
Southern Pine, Select Structural is a dimensional lumber grade with reference design values to NDS 2018 Supplement Table 4B. Its reference bending value Fb is 2,550 psi, compression parallel Fc is 2,000 psi, and modulus of elasticity E is 1,800,000 psi (NDS). Values are shown before adjustment factors; apply the relevant NDS C-factors or EC5 k_mod and γ_M for your load case.
| Fb | Bending | 2,550 psi |
| Ft | Tension parallel | 1,400 psi |
| Fv | Shear parallel | 175 psi |
| Fc⊥ | Compression perpendicular | 565 psi |
| Fc | Compression parallel | 2,000 psi |
| E | Modulus of elasticity | 1,800,000 psi |
| Emin | Modulus for stability | 660,000 psi |
| G | Specific gravity | 0.55 |
| Nominal | Actual (in) | Metric (mm) |
|---|---|---|
| 2x4 | 1.5 x 3.5 | 38 x 89 |
| 2x6 | 1.5 x 5.5 | 38 x 140 |
| 2x8 | 1.5 x 7.25 | 38 x 184 |
| 2x10 | 1.5 x 9.25 | 38 x 235 |
| 2x12 | 1.5 x 11.25 | 38 x 286 |
Southern Pine Table 4B values are size-specific; values shown are the 2x4 basis - see SPIB grading rules for other widths.
Source: NDS 2018 Supplement Table 4B. Reference values are shown before adjustment factors (NDS C-factors / EC5 k_mod, γ_M) - apply these per your load case in design.
Understanding these values
For a beam in Southern Pine, Select Structural, bending at Fb 2,550 psi normally sets the size, but the check that actually governs depends on the span. Short heavily loaded members are often limited by shear at Fv 175 psi, and bearing at a support is limited by compression perpendicular to grain at Fc perp 565 psi, which is the lowest of the strength values and the one most often overlooked. Used as a post or stud, the governing value is compression parallel at Fc 2,000 psi.
Stiffness for Southern Pine, Select Structural is E 1,800,000 psi, with the reduced modulus Emin 660,000 psi used for stability calculations such as the beam stability factor CL and the column stability factor CP. On typical floor spans, deflection rather than strength decides the section, so compare E before Fb when the member is a joist. Its specific gravity of 0.55 is the value connection design works from, not the strength figures.
Within the dimensional lumber entries in this catalogue, Southern Pine, Select Structural is the strongest in bending at 2,550 psi, against 500 psi for Spruce-Pine-Fir, No. 3 at the other end of the range.
The closest alternative in the same family is Southern Pine, No. 1 at 1,850 psi in bending, 38% below this grade. If availability drives the choice rather than capacity, that is the substitution to price first - but re-run the deflection check as well, because stiffness and strength do not always move together.