I'm working on a project to add a second layer of plywood to my shed floor to increase its height. However, I've run into an issue where the screws spin in place towards the end of installation. This has happened with both a 3-inch decking screw and several 1 1/4-inch SPAX construction screws. Even though the screws are still removable and seem to hold the wood together fine, they stick up about 1/16 inch above the surface, which is quite noticeable. I've experienced this problem on other projects as well, such as when attaching decking boards to my porch. I'm curious about why this occurs and what I can do to fix it or prevent it in future projects.
3 Answers
It sounds like you might be pressing down too hard while driving the screws. An impact driver can sometimes pull them in too fast, especially if the material you're attaching isn't thick enough. Just make sure you're giving them enough forward pressure but not too much to let them pull themselves in smoothly. Also, double-check the thickness of the substrate to ensure it's adequate for the screws you're using.
You might want to consider pre-drilling a countersink hole for those screws, especially if they're not driving in flush. Double-check if the screws are threaded all the way to the tip and how thick the total material is that you're screwing into. Sometimes, if the screw hits another screw too deep or if the layers are too thick, it can cause spinning without driving in completely.
Have you been using a drill driver or something more powerful? An impact driver is great, but make sure you're not going full speed right away. Slowing it down can help prevent this problem because it gives the screw a better chance to bite into the wood. Self-driving screws can still benefit from a pilot hole to help get them started in some situations.