This document provides a table listing standard sizes for framing lumber. It shows the nominal and dressed dimensions for various thicknesses and widths of lumber. It also notes that thicknesses may be up to 1/2 inch smaller when rough or surfaced on four sides. Additional sections describe decking dimensions and explain terms like tongue and grooved. Diagrams are included to illustrate different types of wood stresses like horizontal shear, compression perpendicular to grain, and modulus of elasticity. Lumber is typically shipped in multiples of 2 feet lengths for pieces 6 feet and longer.

1. Table 6STANDARD SIZES - FRAMING LUMBER
Nominal & Dressed (Based on Western Lumber Grading Rules)
Dressed Dimensions
Nominal Size Thicknesses & Widths
Thickness Width Surfaced Surfaced Length
Product Description inch inch dry unseasoned feet
inch mm inch mm
2 2 11
⁄2 38 19
⁄16 40
3 3 2 1
⁄2 64 2 9
⁄16 65
4 4 3 1
⁄2 89 3 9
⁄16 90
5 4 1
⁄2 114 4 5
⁄8 117
DIMENSION S4S 6 5 1
⁄2 140 5 5
⁄8 143
8 7 1
⁄4 184 7 1
⁄2 191
10 9 1
⁄4 235 9 1
⁄2 241
12 111
⁄4 289 111
⁄2 292
over 12 3
⁄4 off nominal 19 off nominal 1
⁄2 off nominal 13 off nominal
Thickness Width
unseasoned unseasoned
Rough or S4S 5 and 5 and 1
⁄2″ (13mm) off nominal (S4S).
TIMBERS (shipped larger larger See 3.20 of WWPA Grading
unseasoned) Rules for Rough.
Thickness Width
Thickness Width Dry Dry
inch mm inch mm
2 5 11
⁄2 38 4 102
6 5 127
DECKING 2″ 8 6 3
⁄4 172
(Single T&G) 10 8 3
⁄4 222
12 10 3
⁄4 273
3″ and 4″ 3 6 2 1
⁄2 64 5 1
⁄4 133
(Double T&G) 4 3 1
⁄2 89
Abbreviations: T&G—Tongued and grooved Rough—Unsurfaced S4S—Surfaced four sides
13
Horizontal Shear - Fv
(Fig. 3) Horizontal shear
stresses tend to slide fibers
over each other horizontally.
Most predominate in short,
heavily loaded deep
beams. Increasing beam
cross section decreases
shear stresses.
Compression Perpendicular
to Grain - Fc֊ (Fig. 4)
Where a joist, beam or similar
piece of lumber bears on
supports, the load tends to
compress the fibers. It is
necessary that the bearing
area be sufficient to prevent
excessive side-grain crushing.
Compression Parallel to Grain - Fc (Fig. 5)
In many parts of a structure, stress grades are
used where the loads are supported on the ends
of the pieces. Such uses are as studs, posts,
columns and struts. The internal stress induced by
this kind of loading is the same across the whole
cross section and the fibers are uniformly stressed
parallel to and along the full length of the piece.
Modulus of Elasticity - E (Fig. 6)
The modulus of elasticity is a ratio of the amount a material will deflect
in proportion to an applied load.
Framing Lumber
Horizontal Shear
Fig. 3
side-grain
bearing value
Fig. 4
Fig. 5
E = 2,000,000 psi
Deflection: 1″
E = 1,000,000 psi
Deflection: 2″
Fig. 6
6′ (183 cm)
and longer,
generally
shipped in
multiples of
2′ (61 cm)
6′ (183 cm)
and longer,
generally
shipped in
multiples of
2′ (61 cm)
6′ (183 cm)
and longer,
generally
shipped in
multiples of
2′ (61 cm)
Note on Metrics: Metric equivalents are provided for surfaced (actual) sizes.
© WWPA - 2005