How to Build a Chair From a Single Sheet of Plywood

Lay out the components on the plywood

Using a pencil, lay out all the components that you need to build the chair on your 4×8 plywood sheet. Use a  T-square to draw all straight lines and trammel points for drawing the curves. To ensure accurate dimensions as you lay out the pieces, be sure to account for the 1/8-in. kerf that you will lose with every cut of the blade in between the different pieces.

Make the straight cuts

Strategically make all the straight cuts using a table saw, circular saw, or track saw. If you don’t have a track saw, clamp a straight piece of wood to run the circular saw against to ensure a straight cut.

Cut the arched pieces for the seat and backrest (A), sides (B) and footrest (C) square. Ex: 20-in. x 20-in. or 23-3/4-in. x 23-3/4-in. It’ll make it easier to find a consistant center points and cut the arches. Cut the smaller square spacers (D + E) out of the remaining parts of the sheet on the miter saw after you’ve cut the bigger squares.

Cut the curves

For the arched sides of the seat and backrest (A) and the chair sides (B), use a trim router with a straight-cut bit attached to a router circle jig. Find the center of the squares and set the circle cutting jig to cut a circle with the same diameter as the width of the cut square. Start with shallow cuts, sequentially exposing the tip of the router bit with every pass until you work through the thickness of the material. Be sure to clamp down your plywood as you make cuts with the router. Check the pivot point of the circle jig and the cutting edge of the router bit to ensure you are cutting along the drawn lines.

The footrest arches (C) are laid out the same as the others: find the center of the board, and route an arch that spans from the peak to the centerline on each side. However, to route this swooping arc on a narrow board, the pivot point must be 7-11/16 inches off the board. Be sure to secure the footrest arch piece (C) and whatever substrate the pivot-point nail is stuck into to the bench with zero chance of movement while routing.

Pair and match your arch pieces

Take your arch-cut pieces and pair them up — two backrests (A), two seats (A), and two sets of sides (B). When you have the pairs, clamp them together and run a straight bit with a top bearing along the curved edge of each. This will eliminate any inconsistencies between the two pieces and make them as similar as possible. This is important later when the connecting strips need to be aligned across both faces.

From now on, keep each pair together.

Another thing worth noting is that plywood faces aren’t the same on both sides – one side tends to be lighter, smoother, or cleaner than the other. Select which side you want facing out, and lightly pencil the inside face so you don’t forget. It sounds like a small thing, but when the chair is fully assembled, you’ll notice that one panel is facing the wrong way.

Round over the outer edges

Run a trim router with a 1/4-in. round-over bit along the outer top edge of each arch panel (A, B, and C). Hit the top face only — leave the inside edge square so the connecting strips sit flush and square when you assemble it.

Finish the inside faces

Before gluing anything together, apply a coat of tung oil to the interior faces of all your arch panels (A, B, and C) and all six sides of the connecting spacers (D and E). Once the chair is assembled, you won’t be able to reach these surfaces.

You’ll notice that the oiled plywood looks noticeably different from the raw plywood, which is actually a good visual reminder of what you’ve finished and what you haven’t. Finish the exterior faces and edges of the arched panels (A, B, and C) after the chair is assembled.

Build the seat and backrest slabs

Lay one of the 20-in. arched panels (A) flat on the bench. Starting at the peak of the arch, glue and pin nail small spacers (D) along the curved edge. Use a second spacer (D) to keep a consistent 1-1/2-inch gap between each block.

Shoot 23-ga. pin nails from underneath the arch (A), keeping the nail gun perpendicular to the piece and your fingers out of the way. These tiny pins can shoot out in any direction.

Secure your larger spacers (E) along the flat bottom of the arch panels (A) in the same way — evenly spaced with the same 1-1/2-in. gap between them.

Once all the spacers (D and E) are nailed to the first arch (A), apply glue to the exposed tops of each spacer (D and E), then lay the second arched panel (A) directly on top, closing the sandwich. Secure the second arch (A) with 23-ga. pin nails as well.

Repeat for the other small arched panels (A). You should now have two identical sandwiched slabs — one will become the seat and one the backrest.

Join the seat and backrest

Bring the seat and backrest panels together at a 90-degree angle — the flat bottom edge of the backrest slab meeting the flat back edge of the seat slab. Glue the joint, clamp it, and check square with a speed square before fastening it together with a couple of hidden 1-1/2-in. screws between the large spacers (E) from inside the seat slab. Use a countersink bit so the screw heads sit below the surface of the plywood.

Attach blocks to the side panels

This follows the same process as building the seat and backrest panels — with one key difference. You’re only doing half the sandwich slab for now.
Take one curved piece from each of your large arched panel (B) pairs. Glue and pin nail the small spacer blocks (D) along the curved edge, starting from the center of the arch and working out. Use an extra spacer (D) to keep a consistent 1-1/2-inch gap between each spacer (D). Run the large spacers (E)  along the flat bottom edge the same way.

Unlike the seat and backrest, don’t close these out with the second curved piece yet — set both half-assembled slabs aside for now.

Mark the seat position on the side panels

Take the side-arched panels (B) that don’t have any spacers attached. On each one, draw an angled pencil line connecting two points: 13 inches up from the bottom corner on the back edge, to 15 inches up from the bottom corner on the front edge. The lines don’t need to run the full width — 10 to 15 inches is enough to see them during assembly.

Draw a second line parallel to the first, exactly three inches above it, toward the peak of the arch. These two lines mark the top and bottom faces of where the seat slab will land on the side panel (B).

The point where the lower line starts — 13 inches up the back edge — is where the heel of the seat/backrest “L” assembly will attach.

Flip the panel over and transfer both lines to the other face. This keeps your nails and screws aligned when you’re fastening from either side.

Attach the side panels to the seat assembly

Work one side at a time. Set the seat/backrest “L” assembly on its side and position the side (B) — the one without the spacers (D and E) — on top of it, aligning the seat to the angled lines you drew in step 10. The heel of the seat should sit right at the back edge where your bottom line begins.

Glue the joint, tack it with 18-gauge nails, then drive 1-1/2-in. screws into the connection — aim them at the spacers (D) inside the seat sandwich so they have something solid to bite into. These fasteners will all be hidden once the other side panel (B) is closed over them.

Flip the chair over and repeat on the other side with the other side panel (B). Before you fasten it, double-check that the bottom edge of the arch panel (B) is at the same height as the first side — if they are off by even a slight amount, the chair will rock.

Close the side panels

With the seat/backrest “L” assembly now fastened to both loose side panels (B), close both sides. Take the two half-assembled side panels (B) — the ones with the spacers (D and E) attached — and glue and pin them over the open side of each side panel (B) with 23-gauge pins. Clamp across the full width of each side (B) to pull the edges together flush and let the glue set before moving on.

Build the footrest

Cut 3/4 inches off each end of one of the footrest arch panels so that it is only 18-1/2 inches long. Assemble the footrest together with the two footrest arch panels (C), sandwiching six small spacers (D) along the front edge and three large spacers (E) along the back. Start in the center with both spacers (D and E), and work your way out, keeping them evenly spaced. Use wood glue and 23-gauge pin nails, keeping the same 1-1/2-in. spacing between spacer blocks as everywhere else.

Attach the footrest

Two large spacers (E) should be glued and nailed to the inside arches (B) of the sides, with their tops level, 5-1/4-in. from the bottom of the arch, and flush with the front edge. Install the assembled footrest so that the top 20-in. uncut arch (C) rests on top of the large spacers (E) and finishes at a height of 6 inches. Recess the footrest into the side slabs 3-3/4 inches from the front of the chair. Glue and tack with 18-gauge nails, then drive screws through the side slabs into the footrest, tucking them between the small spacer blocks (D) so they stay hidden.

Fill, sand and finish

The finish is what separates a good build from a great one. Fill all nail holes with wood filler, let it dry completely, then sand it smooth. Apply the first coat of tung oil to all exterior faces, allow it to dry, and lightly sand back the raised grain before applying the second coat. Two coats is the minimum — three won’t hurt.

FAQ

What are the four grades of plywood?

The corresponding letters A – D given to sheets of plywood reflect the quality of the sheet. The quality will also reflect in the price. Different ratings serve different applications: A is the highest quality, the smoothest and results in a paintable surface that won’t diminish the quality of your end product. B: allows for manufacturers to leave minor defects smaller than one inch. C: allows for tight knots and other defects to be visible and not sanded for a smooth finish. D: allows large knotholes and is intended for structural applications that won’t be seen.

Can I find plywood in different species?

Yes, plywood is manufactured in a wide variety of species with the outer veneer reflecting the desired species, i.e. walnut, cherry, birch, etc.  The price will vary greatly based on the species desired and the composition of the inner core of the sheet of goods.

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