Modular Shelf System – FineWoodworking

18 December 2024 Stan

The original version of this shelving unit stood in the home of my childhood friend, Max. It was designed and built by his father, Konrad Rieger, an architect, who received his training at the Berlin University of the Arts in the 1960s. Rieger’s Bauhaus background shines through in the clean functionality of the shelf design. For my own version, I staggered the shelves and varied their lengths and widths, added underbevels to lighten their visual weight, and tweaked a few other details. Just like Rieger’s originals, however, these shelves support rows of heavy art books without sagging.

Easily scaled to fit your space, this modular system is fully adjustable, thanks to a sturdy peg system. It also knocks down and transports easily if you need to relocate it. And unlike many other woodworking projects, the whole thing can be made and installed in a weekend or two.

The project contains helpful lessons as well. You’ll get lots of practice routing mortises with a template and forming smooth bevels with a hand plane.

Feel free to adapt the design

The engineering is what’s most important about this strong, stable system. The shelves get through-mortises so they slide down over the support posts, and thick pegs hold the shelves at various heights. The posts carry the weight to the floor, and the whole assembly is kept upright by fastening two of the full-length shelves to the wall with simple steel angle brackets, which are placed out of view.

I sized the shelves to suit my space, varied their widths to fit the books I own, and staggered them until I found a look I liked. The wider shelves have enough headroom to fit large-format books, and the smallest have 9 in. of clearance for pocket paperbacks. I placed additional peg holes above and below each shelf position, so I can adjust the array if needed.

But the elements are easily altered. Got more paperbacks than I do? Add another narrow shelf. Need an even deeper shelf for audio components or big coffee-table books? Find the widest lumber you can. Have taller items to store or display? Just change the locations of the shelf-peg holes.

If you decide to make an even longer shelf unit, don’t forget to add more support posts. To minimize sagging, space the posts no more than 3 ft. apart, and have the ends of the shelves project 18 in. or less. By the way, I used ash for the shelves and posts, which suits their modernist look. But any hardwood will be great.

Make the shelves first

After milling the shelves to size, I stacked them one on top of the other in their final orientation, adding a few spacer blocks to keep them all level. That let me mark their back edges with centerlines for the locations of the posts. Later, I carried those lines across the top of each shelf.

Make the mortise template

Start by laying out a square mortise in the center of a square piece of plywood, extending the lines to the edges. To form an accurate opening in the template, I clamped the plywood to the top of my table saw, using the rip fence to align it, and brought the sawblade up through the workpiece. To make the plywood easier to clamp down for these plunge cuts, make it larger than needed. After the mortise cuts are made, you can trim it to a more appropriate size.

You’ll need to cut past your layout lines to form each wall of the mortise, but that won’t affect the routing later. Just be sure to cut on the correct side of the lines.

When raising the blade for the last cut, stop a little short so the square in the middle isn’t cut completely loose. Leave just enough of a connection so it won’t rattle around dangerously. Let the blade come to a complete stop, and then cut away the last bit with a handsaw.

With the mortise opening finished, cut the plywood down and screw a cleat onto one edge to reference against the back edges of the shelves.

Using the template—Now clamp the template to a shelf, centering it on one of the mortise centerlines and pressing the cleat against the shelf’s back edge. Before using the router, drill out some waste. This reduces the routing and provides a starter hole for the bearing-guided router bit. I bored these large holes with an auger bit and brace, but a power drill and Forstner bit would also work. Either way, clamp the workpiece to a sacrificial board to keep the exit hole clean.

The support posts have a 1/4-in. roundover on their corners, so to rout mortises with the same exact shape, simply use a 1/2-in.-dia. pattern bit. Use a flush-cutting bit with the bearing located above the cutters.

Plane the big bevels—The 7/8-in.-thick shelves would look pretty clunky with square edges. To lighten their look, I routed 1/4-in. roundovers on the top edges—echoing the roundovers on the support posts—and cut shallow bevels along their lower edges.

You can rout the long bevels with a raised-panel bit, but I prefer to work by hand when I can. So I laid them out in pencil and shaped them with my jack plane.

Bevel the ends of the boards first. That way, any chipout resulting from these cross-grain cuts will be removed when you bevel the long edges.

Make the support posts

Mill the post stock to fit the mortises, and then take off an extra 1/16 in. with the planer. That way, they will slide through the square openings without jamming (after their corners are rounded).

When you are installing the shelves, some will need to be slid down over the tops of the posts. So crosscut the posts roughly a few inches short of your ceiling height.

If your floor is significantly out of level, add adjustable feet to the bottoms of the posts. Otherwise they can stand directly on the floor.

Before rounding the post corners to fit the shelf mortises, lay out the peg holes. Place these as shown above, or base them on your own shelf array. I went with groups of three, spaced 2 in. on center. Spacing the trios of holes about 8-1/2 in. apart will let the shelves accommodate standard book sizes.

To drill the 3/4-in.-dia. holes, I used an auger and hand brace once again. But if you have sufficient outboard space next to your drill press, that machine would also work great. Just be sure to place a sacrificial board below the posts to prevent blowout on the back side.

After boring the peg holes, I routed a 1/4-in. roundover on the posts’ edges and ends. This is easiest to do on the router table.

Fine-tune the shelf pegs

The shelf pegs should be a tiny bit undersize so they are easy to insert. Don’t worry about the wiggle room; once the shelves are loaded, the whole system is self-stabilizing.

I started with 3/4-in. hardwood dowels and cut them to length on the bandsaw. To trim them for a nice fit in their holes, I planed little facets on them. I did this by clamping my jack plane upside down in my vise and passing the dowels over them.

I like the minor irregularities of the planed facets—a little handmade touch for the inquisitive observer. I chamfered the ends of the pegs as well to complete the look.

Finish and install the shelves

To finish the shelves, posts, and pegs, I went with just a few coats of dewaxed shellac to keep the ash as natural-looking as possible. But you can use any finish that suits you.

After the last coat of shellac, I applied a coat of paste wax using #0000 steel wool and then buffed with a clean cotton cloth.

You’ll need an extra set of hands to install the shelf system. Start by stacking the four lower shelves on the floor against the wall, and then slide the posts into the stacked mortises.

Now slide the topmost of those shelves up into position, and insert pegs to hold it there. This is one of the shelves that gets attached to the wall with small metal brackets screwed into the wall studs. Place the brackets on the bottom of the shelf, not too close to the ends, so they aren’t visible from standard viewing angles. Then slide the three lower shelves up into place and insert their pegs.

To install the upper shelves, raise them to ceiling height and slide them down onto the posts. Pick a shelf that is above your eyeline, and attach a set of brackets to the top side, screwing them into the wall studs as before.