| Originally posted on Reddit. See Thread |
For two summers, between semesters in college, I worked for a marine construction company in the Chesapeake Bay area. Our company built living shorelines, laid rip-rap, and built and resurfaced piers. Most of our work was with piers.
I spent most of my summer decking piers. Most times I would be purchasing lumber, hauling lumber, hefting lumber, cutting lumber, holding lumber over my head while standing chest-deep in water with jellyfish literally wrapping themselves around my legs, or screwing lumber into other lumber that was already bolted in place. There were other interesting parts of the job, but this story revolves around lumber.
When we laid a deck on a pier we would screw the deck down onto the supporting parts ("stringers") below. To accomplish this we had what was basically a fully automatic screw-gun on a stick. We could load a literal clip of screws into the device and stroll leisurefully down the deck, driving screws in at a rate of about one every three seconds without even bending over. We had one guy on our crew who could drive home two screws every second. As you might imagine this procedure didn't take much time.
During the first summer we had a customer in the middle of July who was paying us to resurface his pier. All we had to do was rip up the old deck (easier said than done; old wood likes to fragment rather than cooperate), replace any of the underlying structural lumber that had rotted out or been otherwise compromised, and lay down a new deck. Given fair weather this should have been a three-day job.
Unfortunately for everyone involved, Mr. Customer insisted that we nail his deck down, rather than screw it in place. This is the wrong thing to do, for two reasons.
Firstly, it takes a whole lot longer to nail a deck down than to screw it down. As I said, that screw-gun-on-a-stick could bring home one screw every three seconds for a modest worker. It takes five to ten seconds to drive in a nail. Though you could go gorilla-mode and pound that sucker in with two solid strokes, if you miss you'll damage the deck which requires that the board you just engraved with your hammerhead pattern be replaced, so you have to take it steady. Add to this that your laborers are hot and sweaty and their wrists can only take so much. 400 feet of pier amounts to more than five thousand nails so this process expanded the job from three days to five, with extra hours on each. Do you know how much it costs to hire a construction crew for a day?
Secondly, and more importantly, is the fact that nails work very differently from screws. Have you ever noticed that the shaft of a nail is smooth? It's not threaded like a screw, so you can take a hammer to it and drive it straight in to whatever it is you're nailing. Unfortunately this means that it is also possible for that nail to back straight out the way it came - this is the whole premise of the claw on a hammer. Usually this isn't an issue, in places where nails are normally used. If you nail something to your bedroom wall it should stay there for a very long time unless you give it a really good tug.
Outside, where piers are, it gets really hot in July. This wouldn't be a problem except that it also gets really cold in December. Many times each year that pier will get hot, then cold, then hot again. As you might remember from middle school science class, hot things expand and cold things contract. Wood is especially good at this, which is why your house makes sounds at night, because the wood (or the ground underneath it) is cooling and settling in the chilly nighttime air.
After two or three years of this pier breathing all year long, getting wet and then drying out, and being walked on, that wood is going to lose its grip on those nails. Gradually they will lose their grip on the wood. Some of them will slowly come up and be ejected by the deck, while others will simply sit there and pop right up and out the second anything pulls up on them (like when someone stands on the opposite end of the board; imagine a see-saw). Ultimately this guy will end up with a deck that is not at all secured to the pier.
Screws would not have this problem because they're threaded ("Threaded" refers to the spiral running down the shaft of the screw). Those threads will hold on to the wood until it literally rots, which for treated lumber is a very long time. Our company pegged the lifespan of its piers at about eight years before they would need major maintenance.
Our foreman explained both of these concepts to Mr. Customer, that his insisting on nails would increase the immediate cost of the work and more than halve the lifespan of his pier. Mr. Customer decided that he knew better than us, and demanded that we lay his deck with nails.
As a result we got paid to sit on the deck of a pier in the sweltering July sun pounding nails into the deck. We made a little extra cash and got some very nice blisters on our hands, as well as some seriously sore wrists and elbows (wrists for the obvious wrist motion of swinging a hammer, elbows because that's where all of the shock goes when the hammer hits home). I recall my foreman saying that the price tag on the job went up by a pretty huge amount, which of course Mr. Customer paid.
This was about eight years ago now, so I can 100% guarantee that this guy has had to buy a new deck since then, quite possibly two.