While watching one of those TV Hero-Competition Bashing Contractor screwing a deck frame together the other day it illuminated a contentious debate in the Deck Business. Which is stronger… Nails or Screws for decks?
Nails have a much greater sheer strength, while for a short time in a deck application screws may hold tighter. If this surprises you, try this experiment. Put a screw in a nice big block of wood about 1.5” deep…could be firewood, the type doesn’t matter.
Now, hit the screw with a hammer.
It sheers off clean.
Try the same thing with a nail.
You would have to bend the nail back and forth 50 times for it to snap off.
This is why we use Nails for framing.
If it is in the budget to use a joist gasket and stainless screws, we will use them. Or in the case of Pressure Treated, at request of the client, we will use ACQ Screws. However we do let them know that when it comes time to refinish the deck, you may end up changing a number of broken screws even taking these precautions.
When the boards are swelling from moisture it can cause the screws to tear out of the joists leaving a void for moisture to cause premature rot. If the finish was damaged during installation it can corrode. Often the screws will simply not hold beyond a couple of years.
When you refinish a deck typically we set all the nails a quarter inch deep, then sand the deck with a large machine….
If the deck is screwed down, you have to set the screws. This means that roughly half the screws will strip within the joist, or break or the head will strip at the bit. That exposed steel will react with Red Cedar causing black streaks.
Now, In California did you know that it is illegal to assemble your deck with Screws?
Due to earthquakes, screwed frames have collapsed causing injury and damages in several locations. Many things are discovered in California first…
Build Safe gang—Don’t believe what you see on TV when it comes to woodwork.