Prepare the Parts
Lightly sand the cabinet and bookcase units with a palm sander.
Paint or stain the cabinets and bookcases. Choose a color that coordinates with the color palette of the room.
Check that the cabinet knobs match the room’s style. If not, replace them.
Assemble the Base Unit
Check the design of the built-in cabinets by dry fitting the pieces together before screwing them into place. Place the base cabinets along the wall designated for the unit. Stack the bookcases on top. Try different arrangements with the bookcases on top to see which orientation works best in the space. The units can be separated to leave a counter-like opening between the bookcases for a television or display, or they can meet at the center and leave one or both ends without a bookcase, also for decorative features. Remove the bookcases on top, and set them aside.
Affix the base cabinets to the wall. Locate the wall studs with a stud finder and screw the cabinet to the wall through the inside back of the cabinet with 3-inch deck screws.
Screw the side of the first base cabinet into the side of the next base cabinet with 1-inch screws.
Attach all of the base cabinets to the wall with 3-inch screws and to each other with 1-inch screws.
Add the Shelves
Assemble the bookcases across the tops of the base cabinets.
Screw the bottom shelves into the tops of the base cabinets with a drill. Drive screws into the two back corners of the units. Use 1-inch screws if the bottom shelf is flush with the bottom. Use 4-inch screws if the bottom shelf is raised 3 to 3 ½ inches from the bottom.
Screw the bookcases together through their side panels using 1-inch screws.
Trim the Built-In Bookcase
Measure the width of the whole unit. Mark this measurement on 3 strips of wood trim – one for the top, one for the base of the shelves that rests on top of the cabinets and one for the base of the cabinets that rests on the floor.
Cut these pieces with a compound miter saw.
Apply wood glue along the back of each trim piece. Align each piece to the unit, and nail them in place with the pneumatic nailer and brad nails.
Measure the vertical edges of the bookcases and cabinets where they meet.
Transfer this measurement to the wood trim, and cut the pieces with the compound miter saw.
Apply wood glue to the backs of the trim pieces, line them up to the unit and nail them in place.
Touch up the edges and the holes with putty and paint or stain.