Nail pops occur when nail heads pop through the surface of sheetrock walls and create bumps or cracks. Here’s why they happen and how you can fix them if they pop up during your renovation. What Causes Nail Pops? One main cause of nail pops is the movement of wood framing. Over time lumber moves and changes shape ever so slightly as its moisture content fluctuates. During this process the dimensions of the wood—its length, width, and depth—shrink and expand at different rates. This movement causes nails to back out of the drywall and pop through the surface. There are