Modular Masterpiece: Build a Fully Customizable Modular Bookshelf

A stunning wall unit that’s infinitely flexible—customize it to suit your space and your stuff.

Back when I was just starting out in my first apartment, I piled up milk crates to store all my worldly goods. It was a simple idea, and it worked like a charm. Fast-forward many years: Faced with a need to store and display lots more stuff, I made plywood boxes in two sizes and mixed them up, adding doors to some and painting the inside backs of others the same color as my wall. The result was a stunning showcase that’s adaptable to any situation and includes useful storage space.

TIME

Multi-day

COMPLEXITY

Moderate

COST

Over $500

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Create your own design

To plan the unit, I used my kids' LEGO blocks to play around with different patterns (Photo 1), but you could just use paper or cardboard. Before you start, note any outlets or vents along the wall.

Once your design is set, figure out how much plywood you'll need. Each box is composed of five parts: a back (A and E), top and bottom (B and F), and two ends (C and G). You can also add doors (D and H).

Count the number of single and double boxes in your design, then take a look at how many of these pieces you can get from one sheet of plywood (Figure B). The sheet I've drawn yields two single boxes and one double box, but you could cut one sheet into all singles or all doubles or any mix of the two sizes. Birch plywood costs $35 to $50 per sheet; my enormous project required 15 sheets.

In addition to the boxes, you’ll need more plywood to surround the unit on all four sides (J and K; Figure A). These pieces aren’t essential, but they give the unit a clean, finished look by hiding all the seams. And they make all the members look equal in thickness.

You may also need plywood to build a base for the boxes to stand on (L – P; Figure D). This part isn’t essential either (you could stack the boxes directly on the floor), but I definitely recommend it for a large unit like this one. Starting out with a level base—rather than an uneven floor—makes aligning the boxes much easier when you stack them.

Figure A: How parts fit together

Figure B: A typical yield from one sheet of plywood

It's just a bunch of boxes

Cut the plywood to rough size

Building plywood boxes is usually no big deal, but these have to fit together just right. Every square box has to be absolutely square—that is, its height must be exactly the same as its width. And a double box must be exactly twice as long as a single.

If that level of precision sounds intimidating, don’t worry. I’ve worked out a method of cutting, building and assembling the boxes that guarantees success.

Here’s the best strategy for cutting the plywood: Break down your sheets into oversize backs, tops, bottoms and ends first, then cut each of these pieces to final size in batches. You’ll be making “rip cuts” and “crosscuts.” Rip cuts go with the grain and determine a piece’s width; crosscuts go across the grain and determine a piece’s length.

Start by making three cardboard templates using the rough dimensions given in the Cutting List. Cut each piece of plywood into three 16-in.-wide strips, then use the templates to draw every crosscut you intend to make (Photo 2). Label the parts and tally them to be sure you have enough of each kind. Add two extra single-box backs to your list. You’ll need these to build a pair of jigs that are essential for assembling the boxes (Figure C).

Crosscut each strip using a sled on your table saw (Photo 3). Use a 60-tooth or higher crosscut blade to avoid chipping out the face veneers. Learn how to build your own table saw sled. Sort the parts into clearly marked piles. The next step is to make one perfectly straight edge on each part, following the grain. The best method is to rip each part twice—the cut edge will become straighter, and smoother, with each cut you make. First, set your saw’s fence to cut 15-3/4 in. wide, then rip all the pieces from their straightest side (Photo 4). Mark these edges, then reset the fence to 15-1/2 in. and rip each piece again, running the marked edge against the fence. Make a different mark on this new edge to indicate it’s the best one.

Next, cut one square corner on each piece (Photo 5). Make test cuts first to be sure your sled is cutting absolutely square. Be fussy—accuracy will pay off when you assemble the boxes.

Figure C: Squaring jig

Figure D: The base

Cut the parts to final size

The backs determine the overall size of each box, so make them first. Start with the smallest ones—the single-box backs. Begin by setting the saw’s fence to 13-9/16 in., then make a rip cut from the good edge of each single-box back (Photo 6). Rotate each piece 90 degrees and make a crosscut from the other good edge.

This dimension—13-9/16 in.—is repeated in a number of other parts, so it’s best to cut them all at the same time. Crosscut all the single-box tops and bottoms, then rip all the double-box backs at this setting.

Next, cut all the double-box backs to length. It’s better to use actual parts, rather than a ruler, to figure out this dimension (about 28-9/16 in.). The length of a double’s back equals the sum of two single backs plus the thickness of two pieces of plywood. Place these four parts next to your saw’s blade, then butt the saw’s fence next to them. (Use two scraps to represent the plywood’s thickness.) Crosscut all the backs to this length. Cut all the double-box tops and bottoms to this length as well.

Use a similar method to figure out the precise length of all the end pieces (Photo 7). This dimension equals the width of a single-box back plus the thickness of two pieces of plywood. Place these pieces next to the saw’s blade and butt the fence to them. Crosscut all the ends at this setting (about 15 in.). The final cuts determine the outside depth of both boxes. Set the fence to 15-1/4 in. and rip the ends, tops and bottoms at this setting.

Dealing with Outlets and Vents

Don’t cover electrical outlets and air vents—work around them. Plan ahead so a box’s edge won’t cover an outlet. The outlet must sit “inside” a box, accessible through a hole in the box’s back. Cut the hole when you’re stacking the boxes to be sure you put it in the right place.

To allow airflow from a floor vent, add an elbow and extend the duct to the front of the base. Cut a hole in the front of the base to receive the duct and then fasten the vent cover to the base.

Build the boxes

Apply iron-on edging to the fronts of all parts. For tips on that, check out Edge Banding with Iron-on Veneer Edging. I actually cheated and paid $250 to have my parts edged by machine at a cabinet shop.

It’s much easier to finish the boxes before building them than after! I chose a dark stain to hide any small gaps between boxes; using a dark color, gaps just look like shadows.

Build two jigs to help with assembly (Figure C). Start assembling the single and double boxes by attaching a top to a back (Photo 8). Support the top with the jigs. Butt the top up to two stops clamped to the back. Be sure both pieces are aligned side-to-side, then shoot three 1-1/2-in. brads to lock the pieces into place.

Next, drill three pilot holes and drive in screws. The nails prevent the pieces from shifting; the screws pull the parts together. (Tight joints are essential for the boxes to nest together properly.) I used deck screws that have a smooth shank right under the screw’s head. To drill the pilot holes, I used a combination bit and countersank the holes halfway into the top piece of plywood so none of the screw’s threads would engage it—that’s the key to pulling parts tight.

Leave the jigs in place, then turn the assembly over and repeat the procedure for attaching the box’s bottom piece.

Next, reverse the jigs and clamp the open end of the U-shape assembly (Photo 9). Nail and fasten the top of one end piece, making sure front edges are flush. Turn the assembly over. Use a clamp, if necessary, to nudge front edges flush again, then finish nailing and screwing the end. Repeat the procedure for the other end, then remove the jigs.

Endless Possibilities

You can mix and match boxes in any pattern, any size. Think big and you can fit a TV and speakers in between them. Think small and you can fill a short wall with just a few boxes.

Assemble the wall unit

As with building a house, the foundation of this wall unit must be level and straight before you start stacking boxes. The easiest way to do that is to make a ladder-like base (Photo 10 and Figure D). Size the base so that the wall unit will overhang it by 1 in. on all four sides. My base is 4 in. high—just tall enough to raise the wall unit above my baseboard molding. My wall unit was so long that I had to make two bases and screw them together.

After leveling the base, make a “skin” of stained and finished plywood pieces to cover the screw holes in the base. Rip the skin pieces extra wide so you can scribe them to the floor, covering the gaps where the base is shimmed. The skin is mitered at the corners and nailed to the base. Screw one plywood piece or pieces to the base to create a shelf for stacking the boxes. The length of this shelf must equal the length of the bottom row of boxes. To figure it out, temporarily clamp together a row of boxes and measure it.

Assemble the first couple of rows on the shelf (Photo 11). Use clamps to temporarily hold the boxes together, then shift individual boxes as needed to align their front edges. When things look good, fasten the boxes together with drywall screws. Their black heads will be almost invisible.

Complete stacking one end of your wall unit and add an end cap (Photo 12). Fasten the cap from inside the boxes.

Fill in the remaining boxes, working from the end cap over. You may need to shim here and there to keep edges aligned. I used rubber electrical tape for shimming. It’s a hefty 1/32 in. thick, black all the way through, and sticks anywhere.

Fasten a few of the boxes to studs in your wall so there’s no chance of the unit toppling forward. Top the boxes with another piece of plywood to preserve a “double wall” look throughout the unit.

Easy, Invisible Hinges

To complement the unit’s sleek, modern look, I wanted the door’s hinges to be hidden from the outside. Euro-style hinges are the way to go.

Euro hinges may look complicated, but that’s just because they’re fully adjustable. After you install them, you can easily even up the gap around a door simply by turning some small screws on the hinges.

Installing Euro hinges is pretty darn simple, but you’ll need a 35mm (1-3/8-in.) Forstner bit. A template for locating the hinge holes is handy too. You can get both in one package at woodcraft.com (DrillRite Hinge Jig and Bit, No. 143958). I used Blum 110-degree soft-close hinges (B071B3650) and Blum 9mm clip mounting plates (B175H719).

Super-tune your sled

I always use a sled to cut plywood panels on my table saw. Learn how to build a table sled.

A sled is supposed to guarantee a square cut, and truly square cuts are essential for the boxes of this wall unit to stack properly. Was my sled really that accurate? I’ve checked panels I’ve cut with a combination square and they seemed OK, but before building these boxes I put my sled to the ultimate test (Photos 1 and 2).

The result? My sled was off just a teensy bit. The best solution is to readjust the sled’s fence, but, in a hurry, I just shimmed it with a few layers of tape (Photo 3). Now it’s dead-on perfect.

Photo 1: Cut two pieces

To check your sled’s accuracy, cut two large pieces of plywood from the same side of the sled’s fence. Stack the pieces on top of each other with the newly sawn edges facing the same way. Lay the stack against the table saw or other straight edge, then flip the top piece over—like opening a book.

Photo 2: Look for a gap

If there’s no gap, your sled is producing perfect cuts. A gap shows you twice the amount of error the cut deviates from 90 degrees.

Photo 3: Adjust with tape

To correct the angle, add tape to the sled’s fence one piece at a time. Repeat the flip test and add or subtract tape until the gap disappears.

Additional Information

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Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • 3/4-in. birch plywood
  • Edging tape
  • 1-1/4-in. deck screws
  • 1-1/4-in. coarse-thread drywall screws
  • Electrical tape (for shimming)

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