Measure the space where the built-ins will go to determine the height and width of the shelving units. Bookshelves and storage shelves will sag under the weight of their contents and a smaller span will reduce potential sag, so take this into account when laying out your shelves. According to Woodbin.com, a practical span for a three-quarters inch thick shelf is 30 to 36 inches and the proper depth for a general shelving unit is 10 to 12 inches.
Determine how you will finish the shelves at the floor and ceiling. Will you carry baseboard and crown molding across the front to match what is in the room and give it a truly built-in look? Or will you keep it shy of the ceiling and build a toe kick at the bottom for a furniture look?
Will you paint or stain the shelving unit, or will you build it out of pre-finished material?
These questions will determine what materials you purchase to construct the shelving unit.
Size the material you’ve selected for the sides, tops and bottoms to the appropriate lengths and widths with your table saw or skill saw. Rip strips for cleats that will support the bottom shelf. The width of the cleats for the bottom shelf should be a quarter-inch taller than your baseboard for a built-in look and should be no more than 4 inches high for a furniture look.
Drill the holes for the shelf supports with a store-bought or homemade template or use your router and a straight bit to make a dado for a shelf clip track. Install the shelf clip track.
Assemble the case using an air nailer with 1 1/4-inch nails and 1 1/4-inch cabinet screws for added strength. Begin by applying the cleats for the bottom shelf along the bottom of the case sides. Nail, then screw, the bottom shelf to the cleats and case sides. Nail then screw the top shelf to the cabinet sides.
Size the quarter-inch backer material (either plywood or melamine) to match the exterior dimension of the shelving unit and attach using wood glue and 1-inch nails.
Locate the studs in the wall where the built-in shelving is to go. Transfer these marks to the interior of the cabinet and drill pilot holes for the 3-inch cabinet screws with a three-sixteenths inch drill bit.
Place the shelving unit in the space and check to be sure it is level and plumb, adjust the cabinet as necessary. Once level and plumb, attach it to the wall using 3-inch cabinet screws.
Measure and properly size face frame material to cover the exposed edges of the shelving unit. Attach it to the cabinet face with glue and the air nailer using 1 1/4-inch nails. Fill the holes with wood filler and sand when dry.
Measure the interior depth of the cabinet for your shelves. Subtract one-eighth of an inch to allow for side clearance and subtract the thickness of the face molding plus one-eighth of an inch to ensure clearance front to back.
Size the shelves and face material and apply with glue and the air nailer using 1 1/4-inch nails.
Insert shelf pins or clips in the appropriate holes or slots and install the shelves to complete the built-in shelving unit.