Before we begin our discussion on screws and nails, let’s be clear on one thing. The key to successful building, whether it be a backyard deck, or pair of book ends, is not only related to the proper nail or screw holding things together, but whether it was glued or not.
Wood studs, joists, and to a lesser extent plywood, will generally shrink over the first few months after installation, due to moisture loss. Then, as we create humidity in the home by cooking, showering, and just plain breathing, these wood products start to re-absorb some of that lost moisture.
This give and take scenario is a natural process that won’t affect the strength of a product, but it might compromise the joint, leading to popped nails and screws, and certainly the odd squeak. So, unless the plan is to dismantle your project at some point in the future, make that wood to wood, wood to plywood, or wood to composite connection (be it cement board or MDF molding and paneling), as solid as possible by adding the appropriate glue.
Most gluing jobs can be handled by keeping two types of glue in the shop cupboard. That being a bottle of yellow, all-purpose glue, and a few tubes of PL premium, for all exterior, or heavier duty type connections.
Generally, we nail for one of three reasons. Because the shear strength (force required to bend, tear, or break) of a nail, is superior to that of a screw, nails are often required by code when fastening joists to a ledger board, as in the case of a deck, or when laminating lumber together to form a beam. Nails also, on average, have a smaller head than screws, making them less visible, and more easily hidden when performing finishing work.
Finally, nails don’t require electrical power, but only a swift swing of the hammer, keen focus on the nail, and a thumb that knows when to get out of the way, in order to effectively insert.
For everything else, we use screws.
Now, there are hundreds of types of screws. However, choosing the right screw for the job has been made easy due to the fact the name of the screw usually corresponds with the product you’re working with. As a result, if you’re hanging drywall, you’d request drywall screws. If you’re finishing around your shower with a cement board underlayment, you’ll require cement board screws. Regular lumber and plywood will require wood screws. Treated lumber? Either green or brown treated screws of course, depending on what color of decking material you’ve chosen.
The only other information the salesperson serving you will require is the desired length, which if you’re not sure, has equally become a pretty standard thing. So, there’s no more asking for a Robertson or Philips type of screw, with a specific diameter, and desired length. Screws have become so product specific that we automatically suggest to you a 1-1/4 inch, #6, Philips screw if you’re hanging 1/2 inch drywall, and a 2-1/2 inch, #8, Robertson screw if you’re to be fastening down deck boards.
Can screws be mixed? Or in other words, is there great risk in using a decking screw to fasten drywall, and vice versa. Worst case scenario is that the sky thunders, clouds separate, then bolts of lightning descend, turning your pathetic, mortal being into nothing more than a heap of ashes. Best case scenario is that the screw tears the finished surface, or rusts, and eventually fails.
Basically, we don’t mix screws. Screws used for treated lumber have a ceramic coated finish, in order to avoid corrosion from the chemicals in the wood, and rust from the elements. Concrete screws (a.k.a. Tapcons) have a finer, double-thread that effectively holds in the hard, brittle type of conditions found in cement, while drywall screws have a thinly tapered head that best suits the paper surface of drywall.
A screw or nail for every task.