Plaster walls can be a tricky place to hang shelves. If not done properly, the shelves and their contents may come crashing down without warning. With a little care and planning, even shelves mounted to difficult surfaces such as plaster can be hung safely and securely, providing your home with functional and decorative storage.
Determine where you want your shelves and how wide they will be. Shelves that are expected to hold any appreciable amount of weight should be wide enough to anchor to wall studs in at least two places. Wall studs generally are 16 inches apart, but this may vary slightly.
Use a stud finder to locate the studs within the walls. There are many different kinds of stud finders, so follow the manufacturer's directions for the one you have. Locate the vertical studs in the area where you want to put up the shelves and mark the location of each stud.
Determine the height for the first shelf. Mount or hold the laser level so that it makes a line where the first shelf goes. This light shows you where to line up the top of all brackets for that shelf.
Place a bracket over the stud, with the top even with the laser line. Mark the wall where the bracket holes are to be drilled. Repeat this for each bracket for the first shelf.
Drill small pilot holes at each marked location. If the hole goes into a stud, a tiny pilot hole is all that is required. If the hole goes through the plaster and into the hollow space behind it, drill a larger hole for the molly or toggle bolt. Check the instructions that came with the bolts to see what size hole you need to drill.
Screw the bracket into place. If it is being mounted to a stud, use wood screws. If it is being mounted to the plaster wall, use a molly or toggle bolt. When working with molly or toggle bolts, screw them in until the back part has expanded completely and is securely holding the bracket to the plaster wall. Over-tightening can damage the plaster, so stop once the bolt is secure.
Repeat for all brackets, then place the shelf on the brackets. This process can be repeated as many times as necessary to complete the project.