1994 UBC:

Nail should “not fracture the surface of the sheathing”

1997 UBC:

The “head or crown of the nail is flush with the surface of the sheathing”

Overdriven nails reduce shear wall strength

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INSTALL NAILS FLUSH TO THE SHEATHING

• The 1994 UBC stated that the nail should “not fracture the surface of the sheathing”.

• The 1997 UBC has clarified the language to state that the “head or crown of the nail is flush with the surface of the sheathing.”
  • Nails installed with their heads resting on but not into the sheathing can cause problems for roofing and other finishes.
  • Nails should be driven so that the top of the nail is flush and not above the surface of the sheathing.

• What happens during an earthquake?
  • Nails will try to pull through the thickness of wood structural panel sheathing during an earthquake
  • For this reason, it is important that nails should be driven flush with the surface of the sheathing and not overdriven and that they be placed correctly
  • Overdriven nails:
    • Reduce the shear wall strength by effectively reducing the thickness of the sheathing.
    • At panel edges, overdriven nails allow easier nail punch-through.
    • At intermediate studs, overdriven nails allow easier panel buckling.
  • Why are nails overdriven?
    • Excessive air pressure in the nail gun
    • Too long of a driving pin on the nail gun.
    • When the spacing and framing member thickness allow, nails should be added to replace any overdriven nails.