If you screw your backer into the ply and into the joist six inches over it will cause inconsistent movement – no good. Do not screw your backerboard into your joists. After I have all my floor down I will go back and double the screws around every seam. Shop cement board screws in the screws section of Lowes.com. Find quality cement board screws online or in store. Skip to main content Skip to main navigation. May 30, 2011 · Drill the holes so that the screw threads will be anchored in the wall studs - not just the Hardiplank or sheathing. The Hardiplank itself is too brittle to hold a lot of additional weight or wind loading.