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I'm curious what the difference is between these two screws and when one should be used over the other. And are deck screws also referred to as construction screws?

As far as I can tell by visually looking it appears deck screws are galvanized for outdoor use to avoid rusting, but is that the only thing? Are their other smaller subtleties I'm missing?

I'm just curious what screws to purchase for different projects if it even matters in the long run. I know drywall screws aren't really meant for anything else due to their brittleness.

  • If you meant to link or show a pic, it didn't work. Deck screws <> construction screws, though they're sometimes interchangeable. Deck specific screws will often have the top 3/4" reverse threaded to help with pull-down. – Aloysius Defenestrate Aug 20 '16 at 14:13
  • I would recommend stainless steel screws for any/all outdoor applications. For large projects (like decks) they come with a square drive, more positive/less slippage than Phillips head when using powered driver. "Deck" screws are just specialty wood screws. – Jimmy Fix-it Aug 20 '16 at 15:20
  • Deck screws are sometimes also coated in a specific fashion to deal with pressure treated lumber corrosion better than normal galvanizing. – Ecnerwal Aug 20 '16 at 15:38
  • @Ecnerwal pressure treated wood corrodes screws? – ohmmy Aug 20 '16 at 16:40
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Most(all?) screws have a corrosion delaying treatment on them, what used to be considered outdoor decking screws are now constructions screws (the gold screws) due to the change in pressure treated wood chemicals.

The corrosion delaying treatment on modern decking screws has been changed to accommodate ACQ treatment, which is significantly more corrosive than CCA (the old way to treat lumber). This is also why when building a deck you have to use hot dipped galvanized (HDG) bolts and brackets as opposed to electro plated zinc (the shiny ones).

You'll notice on construction screw boxes a red circle with a bar across the letters ACQ, this means they are not suitable for pressure treated lumber as the chemicals with quickly corrode the sacrificial layer.

As an aside, drywall screws are also heavily used in cabinet making because of their thin shafts, it removes the requirement of a pilot hole.

  • Thanks for your response Chris. Which screws would be recommended when building something like a garage workbench? Wood screws or would dry wall screws suffice? – ohmmy Aug 20 '16 at 19:10
  • Workbench? If you're using ebonistry techniques, drywall will suffice, if you're not planning to be technically inclined in cabinetry, your safer bet is construction/wood screws. – Chris Aug 20 '16 at 19:14
  • Lol the previous owners left a jar full of drywall screws so I wondered if they'd be good enough or not. So to clarify, wood and construction screws differentiate by the coating? Or are they threaded differently as well? – ohmmy Aug 20 '16 at 19:29
  • You can get coated screws in pretty much any threading, shaft size, or head type. Effectively, construction screws are a type of wood screw. – Chris Aug 20 '16 at 19:46
  • Some epoxy coated screws are far superior to hot dipped galvinised for modern anti rot treatments. – Ed Beal Aug 20 '16 at 22:14
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The other answered addressed the coatings of the screws, but there are other important factors:

  1. Screws have to have a correct thread. E.g. a regular wood screw would preform poorly in a MDF or fiberboard, you need to use a screw specifically designed for that application.

  2. Screws have to be of a correct length for the application. Notice the smooth part of 2" or longer screws? It helps to pull two boards together. When the screw is too long, it's obvious, but when it's too short, it might appear to work, but if you don't have enough grab, it will fail sooner than later.

  3. Shearing strength. Regular wood screws are very weak when shearing forces are involved. They are great if the boards are being pulled apart, but if there are forces applied perpendicularly to the screw, they don't perform very well. Drywall screws are even worse, by the way. You need to use what's called a "structural screw", which are designed for this application.

Don't get me wrong.... If you're building something simple and cheap, any screw will do... But if, say, you're building a deck and hanging joists with regular wood screws, you might have a very costly and potentially dangerous surprise.

  • So how does one choose the correct screw for particular project? When it comes to wood screws, deck/construction screws where it's not easily evident which ones you're using – ohmmy Aug 21 '16 at 21:08
  • Well, you learn... Like books on woodworking, construction, etc. If you're using particular hardware, manufacturer might specify what screws you have to use. E.g. Simpson's StrongTie metal connectors require Simpson Structural screws and not wood screws. It also depends on the project. When it's a temporary sawhorse, I'd use whatever I have at hand. If it's something expensive or safety-critical, I'd do my research, and look for fasteners appropriate for that specific application. – haimg Aug 21 '16 at 21:24

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