Lumber & Wood Design Values — OpenSpecEngineering

Nominal & Dressed Sizes, Section Properties

Dressed (S4S) dry sizes. A, S and I are calculated from the dressed b × d; x-x is the strong axis.

Nominal size

Nominal	Dressed b × d (in)	Dressed (mm)	A (in²)	S_x (in³)	I_x (in⁴)	S_y (in³)	I_y (in⁴)

NDS 2018 Supplement Tables 4A–4F, in psi: normal load duration and dry service unless the row says otherwise, before the adjustment factors below.

NDS table

Species or group

Grade

Size class

Every row as printed, in psi. G is the oven-dry specific gravity; agency is the grading rules agency.

Show table

Table 4A: visually graded dimension lumber, 2″–4″ thick (psi)
Species	Grade	Size class	F_b	F_t	F_v	F_c⊥	F_c	E	E_min	G	Agency

Table 4B: visually graded Southern Pine dimension lumber, 2″–4″ thick (psi); size factors are built into the width groups
Species	Grade	Size class	F_b	F_t	F_v	F_c⊥	F_c	E	E_min	G	Agency

Table 4C: mechanically graded dimension lumber, 2″ and less thick, 2″ and wider (psi)
Method	Grade	F_b	F_t	F_c	E	E_min	Agency

Table 4C, footnote 2: G, F_v and F_c⊥ (psi) of MSR and MEL lumber by species and E. *1.8E stamped G = 0.55: F_v 175, F_c⊥ 565.
Species	E (10⁶ psi)	G	F_v	F_c⊥	Agency

Table 4D: visually graded timbers, 5″ × 5″ and larger (psi)
Species	Grade	Size class	F_b	F_t	F_v	F_c⊥	F_c	E	E_min	G	Agency

Table 4E: visually graded decking (psi); F_b is for 4″ thick decking
Species	Grade	Size class	F_b single	(F_b)(C_r) repetitive	F_c⊥	E	E_min	G	Agency

Table 4F: non-North American visually graded dimension lumber, 2″–4″ thick (psi)
Species	Grade	Size class	F_b	F_t	F_v	F_c⊥	F_c	E	E_min	G	Agency

From the adjustment-factor pages of each NDS Supplement table. Multiply the reference value by every factor that applies.

Size factor C_F, Tables 4A and 4F, by nominal width
Grades	Width	F_b, thickness		F_t	F_c
Grades	Width	2″ & 3″	4″	F_t	F_c

Size factor C_F, Tables 4B, 4D and 4E (d = actual depth, in)
Table	Applies to	Property	C_F

C_F = (12/d)^1/9, calculated
d (in)	d (mm)	C_F

Wet service factor C_M, moisture content over 19 % for an extended time
Table	F_b	F_t	F_v	F_c⊥	F_c	E, E_min	Exceptions

Flat use factor C_fu on F_b, dimension lumber loaded on the wide face
Width	Tables 4A, 4B, 4F, thickness		Table 4C, 2″ thick
Width	2″ & 3″	4″	Table 4C, 2″ thick

Flat use factor C_fu, Table 4D Beams and Stringers loaded on the wide face (decking, Table 4E, is already flatwise)
Grade	F_b	E, E_min	Other properties

Repetitive member factor C_r on F_b
Table	C_r	Applies to

Spruce Pine (SPIB rules): factors on the Mixed Southern Pine values of Tables 4B and 4D, then E rounded to the nearest 100,000 psi, E_min to the nearest 10,000 psi, F_v and F_c⊥ down to a multiple of 5 psi, F_b, F_t and F_c down to a multiple of 50 psi (25 psi below 1,000 psi)
F_b	F_t	F_v	F_c⊥	F_c	E, E_min

NDS Table 2.3.2. Applies to F_b and F_v, not to E or E_min; use the C_D of the shortest-duration load in the combination.

Load duration	Typical design load	C_D