responds: The coatings on power-driven nails
are plastic polymers known as "thermoplastics."
Their main purpose is lubrication: When the nail is
driven, they melt from the heat of friction, making
the nail slippery so it’s easier to drive.
This allows the nail-gun to be built smaller and
When the coating cools, the plastic rehardens
and creates a bond between the nail and the wood,
so that the nail is harder to pull out.
We’ve confirmed the added withdrawal
resistance of coated gun-driven nails in laboratory
testing here at Clemson, using machines to measure
the pull-out resistance of individual nails.
We’ve also tested assemblies by nailing a
whole panel to framing and applying a suction
pressure to the panel. In both kinds of tests,
coated gun nails hold better than hand-driven nails
of the same size.
If it seems easier to carpenters in the field to
pull out a gun-driven nail than a hand nail, maybe
that’s because of a difference in the way
the different types of nails let go. With a coated
gun nail, once the bond between the coating and the
wood breaks, it’s all over —
after that, you just have a loose nail in a
slippery hole. When a hand-driven common nail is
pulled partway out, the part that is still in the
wood is holding as tightly as it was before, so you
need to keep pulling hard to get it completely out.
But in terms of the strength of a building, I think
the fact that it takes more force initially to get
the coated gun nail loose than it does to pull out
the hand-driven nail is more important than the
suddenness of the way the coated nail finally gives
Keep in mind here, we’re comparing
nails of the same size. These days, not all the
"eight-penny nails" on the market are the same
length and thickness. You can buy gun-driven nails
that are as long and as thick as the hand-driven
common nails they’re meant to replace (in
areas covered by seismic codes, you may have to).
But you could also just go by the withdrawal
strength of the nails, rather than by their size.
Most manufacturers have received National
Evaluation Reports (NERs) from the Council of
American Building Officials (CABO) that specify how
their gun-driven nails or staples can be used in
place of the common nails the code is based on. If
you need the data that’s in the NER, ask
the manufacturer for a copy, or contact the
International Staple, Nail and Tool Association
(ISANTA) at 312/644-0828.
If you want extra holding power, go with a
ring-shank or screw-shank nail. Tests show that
modified-shank nails hold much better than
smooth-shank nails — and if
they’re coated too, that’s just
icing on the cake.
In practice, major failures of nailed
assemblies, such as the building collapses that
happened during Hurricane Andrew, can usually be
traced to the way the fasteners were used, not the
type of fastener. Make sure you hit the framing
(sometimes it’s hard to tell). Put the
nails close enough together —
it’s better to use too many than too few.
And set the pressure on your gun to drive the nails
flush with the surface, not below it. Overdriving a
nail or staple makes for a weaker connection.
Scott Schiff directs building research in
the Department of Civil Engineering at Clemson
University, Clemson, S.C.