Like any tool---pneumatic nail guns can be misused.
Having spent a good part of my life framing houses, I would argue that for framing---nail guns are of little value. Sure they are faster, but you still have to lug a hammer around to drive things into proper position anyway. I know that I am not going to get much agreement about this but I will gladly tilt at this windmill regardless. I have worked side by side guys with nail guns and they never finished what they were doing before I finished what I was doing and the work was certainly never as good.
A guy and his hammer can climb around on a house without dragging hoses and heavy guns around and even nail one handed if necessary. A proficient carpenter can start a 16 penny nail and finish it with one whack---maybe two depending on what kinds of materials are being nailed. Only a novice would take more than one whack to drive sheathing nails once they are started
That said nail guns are awesome for interior finish work. It is very difficult to compete with them by hand nailing.
But this diversion is distracting me from talking about nail guns.
On a recent inspection of a roof I noticed that there were many nail heads sticking through the roof surface.
On my planet I would not allow the use of nail guns to install asphalt shingles. To properly nail a roof shingle the pressure of the nail gun must be set such that it neither drives the nail through the shingle nor leaves the nail head sticking up. This is much more difficult than one much think because it takes much less pressure to drive a nail into the roof near a rafter or truss than it does in the field between the rafters or trusses. The nail tends to "bounce" more and ends up not driven all the way in. Hand nailing can adjust for the differences in amounts of pressure required to drive the nail properly.
With thicker roof sheathings the reverse can happen, where the pressure is OK for driving the nails in the field area but won't push the nail into the truss or rafter. Add to this problem that if the roofer does not hold the gun so that it is directly perpendicular to the roof, the nail will be driven at an angle. The angled head will then, over time, work its way through the shingle that is covering the nail head.
Roofs with this condition will often have shingles that lift up easily because the adhesive strip was never able to function properly due to the nail heads holding the shingles up as in the following picture.
Can you see the nail sticking up jut to the left of my thumb?
So while nail guns "can" be used properly---they often are not.
Charles Buell, Seattle Home Inspector
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WA State, Home Inspector Advisory Licensing Board