This video demonstrates the shear strength of a standard construction nail, compared to a deck screw. The screw snaps off after a couple twists, but the nail remains intact and in the wood after multiple twists. This test clearly shows that nails are the better choice for structural construction framing where joints and lumber can shift and twist.
But don’t write off screws altogether. They have stronger holding abilities (tensile strength) than nails and can draw pieces together.
The best example for when to use a nail versus screw is building a deck. Nails are used to attach the joists to the deck framing, and screws are used to fasten the deck to the frame.
Nails will also work themselves out on decking. Not fun when you go barefoot.
I've built a lot of outdoor projects. My $.02… If you can screw it together, do it. Get the right size screw for the job and strength is not an issue.
Screwing pulls together things with great strength and allows for you to repair things much easier. It's longer to do so, but I prefer it.
Agreeing with Mike & Mike, I generally prefer to use screws when possible (I was gonna say 'screwing', but it sounded all Waco Kid-like).
For production purposes, Bostitch has full-head [a href="http://www.cpobostitch.com/bostitch-c8dr131-hq-2-1-2-in–x-0-131-in–hurriquake-coated-framing-nails–4-000-pack-/bstnc8dr131-hq,default,pd.html"%5Dframing and sheathing nail[/a] that combine advantages from both fasteners.
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