Homeowners often have difficulty locating the studs underneath painted drywall. One option is to bash a hole in the wall and feel around, but there are cleaner and easier methods for finding studs, so employ that as a last resort. Another option is to tap a thin nail in multiple spots across the drywall. If you encounter resistance, you found a stud. The major downside to both these methods is you'll have to repair the damage later.
If you know how far apart the studs are, you only need to locate one to determine where the rest are. Building codes often have specific requirements for stud spacing. Contact your local building department to learn what methods the builders of your home likely used. Typically, the centres of the studs will be either 16 or 24 inches apart. If you can, look in an unfinished attic or crawlspace to determine what methods the builders used.
A stud finder is a device that beeps when held over a section of drywall that has a stud underneath. The simplest models use a small magnet to detect the metal screws or nails used to attach drywall to the wood frame. More advanced models detect the density of the studs and the edges of the wood studs. Typically, you slide the stud finder across the surface of a wall or ceiling, and a noise or light indicates the location of the studs. These devices don't work well for atypical walls or ceilings. For example, if your home has a double layer of drywall for sound- or fireproofing reasons, the detector might not function correctly.
Another option is to pull away a small section of trim near the bottom of a wall. Drywall installers shift the boards up toward the top of the wall, which sometimes leaves a small gap at the bottom. The gap might be large enough for you to spot the bottom portions of the studs.
If you know the thickness of the drywall in your home, you might guess the stud spacing. Of course, the success of this method depends on whether the builders followed standard practices. Typically, 1/4-, 3/8- and 1/2-inch thick drywall all require 16-inch on-centre stud spacing; otherwise the boards will sag and bow. Drywall that is 5/8-inch thick only requires 24-inch on-centre stud spacing; 5/8-inch drywall is common in garages and around heating and cooling equipment because of building codes, which often require enhanced fireproofing measures in those areas.