WORLD FOR CIVIL

Fasteners for wood

Nails and Spikes

The allowable withdrawal load per inch (25.4 mm) of penetration of a common nail or spike driven into side grain
(perpendicular to fibers) of seasoned wood, or unseasoned wood that remains wet, is

p=1,380G^5/2D

where
= p allowable load per inch (mm) of penetration into member receiving point, lb (N)

D= diameter of nail or spike, in (mm)

G= specific gravity of wood, oven dry

The total allowable lateral load for a nail or spike driven into side grain of seasoned wood is

p=CD^3/2

where
p= allowable load per nail or spike, lb (N)

D =diameter of nail or spike, in (mm)

C = coefficient dependent on group number of wood

Values of C for the four groups into which stress-grade lumber is classified are

Group I:: C= 2,040
Group II: : C= 1,650
Group III: :C= 1,350
Group IV: :C= 1,080

The loads apply where the nail or spike penetrates into the member, receiving its point at least 10 diameters for Group I species, 11 diameters for Group II species, 13 diameters for Group III species, and 14 diameters for Group IV species. Allowable loads for lesser penetrations are directly propor- tional to the penetration, but the penetration must be at least one-third that specified.

Wood Screws

The allowable withdrawal load per inch (mm) of penetration of the threaded portion of a wood screw into side grain of seasoned wood that remains dry is

p=2,850G²D

where
p= allowable load per inch (mm) of penetration of threaded portion into member receiving point,
lb (N)

D =diameter of wood screw, in (mm)

G =specific gravity of wood, oven dry Wood screws should not be loaded in withdrawal from end grain.

The total allowable lateral load for wood screws driven into the side grain of seasoned wood which remains dry is

p =CD²

where
p= allowable load per wood screw, lb (N)

D= diameter of wood screw, in (mm)

C =coefficient dependent on group number of wood

Species	Group No:	G	G2	G5/2
Douglas fir	II	0.51	0.260	0.186
Pine, southern	II	0.59	0.348	0.267
Hemlock, western	III	0.44	0.194	0.128
Hemlock, eastern	IV	0.43	0.185	0.121
Pine, Norway	III	0.47	0.221	0.151

Values of C for the four groups into which stress-grade lumber is classified are

Group I: C= 4,800
Group II: C= 3,960
Group III: C= 3,240
Group IV: C= 2,520

The allowable lateral load for wood screws driven into end grain is two-thirds that given for side grain.