Although builders can install plaster or stucco over solid walls, such as concrete block walls, most plaster adheres to wooden strips, called lath, that cover a hollow, wood-framed wall. Concealed beneath plaster, wood-framed walls consist of upright framing members called studs. Although the most secure method of attaching shelves to a hollow wall is to directly anchor shelf hardware to studs, studs are sometimes difficult to find or located in the wrong spot for a particular shelf design. To attach shelf hardware to the hollow portion of a plaster wall, you can use specially designed anchoring hardware called hollow-wall anchors.
Hold a shelf bracket or shelf standard against the wall in the desired position of the shelving unit. Place a level against the side of the bracket or standard and adjust the hardware to a vertical position. Press the tip of a pencil through the bracket or standard's screw holes and mark the positions of the screw holes on the plaster's surface.
Turn the level to a horizontal position, position the level over the top screw hole mark and use the level's edge to mark the location of the second bracket's or standard's top screw hole. Align the top screw hole of the shelf hardware over the second, top screw hole mark. Hold the level against the side of the hardware and vertically level the bracket or standard. Use a pencil to lay out the position of the remaining screw holes.
Attach a twist bit to a power drill. Place the bit's point onto a screw hole mark and gently depress the drill's trigger to start the hole; starting the hole slowly reduces damage to the plaster. Continue drilling until the bit passes through the plaster and into the wall's cavity. Drill holes through the remaining screw hole marks.
Thread the screws for toggle bolts through shelf hardware and into the toggle base prior to inserting the anchor into the hole. Press the toggles through the screw holes and tighten the toggle bolt screws with a screwdriver to secure the shelf hardware to the wall. If you are using expansion anchors, insert an anchor into each hole and align the shelf hardware over the anchors' shafts. While holding the hardware in position, use a power drill equipped with a driver bit to drive a screw through the hardware and into each expansion anchor.
Place a piece of shelving material across the secured shelf brackets. Working from the underside of the shelf, use a power drill equipped with a driver bit to drive screws through the bracket's holes and into the shelving material. If you are using shelf standards, insert the clips of shelf standard hardware into corresponding standard slots. Place shelving material directly on top of the shelf standard hardware's flat, top surface.
Check your hollow wall anchor manufacturer's guidelines for recommended drill bit sizes; using drill bits that are too small or too large can prevent proper installation. Although several types of hollow wall anchors are suitable for plaster walls, the varieties that fully pass through a wall and grab onto the wall's interior face, such as toggle bolts and expansion anchors, reduce cracking and surface damage to plaster.