How to build an octagonal box out of wood

Written by kasandra rose
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How to build an octagonal box out of wood
Octagonal shapes require more cutting than square ones. (Eight-square wooden frame, isolated on white background image by Nikolai Sorokin from

Decorative boxes add interest and utility to the garden. Fill the boxes with unusual objects, use them for storage, paint them colourfully or place potted plants in them or on them. Octagonal boxes are slightly more challenging to cut but provide a different shape to please the eye. Fill sideways stacks of octagonal boxes with garden gnomes, beach balls or gazing balls to add a bit of whimsy to the garden.

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Things you need

  • 2.5 by 20 cm (1 by 8 inch) wooden boards
  • Measuring stick
  • Table saw
  • Adjustable web clamp
  • Drill
  • 1.8 cm (3/4 inch) wood screws
  • 1.8 cm (3/4 inch) plywood
  • 1.8 cm (3/4 inch) finishing nails

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  1. 1

    Cut eight 32.5 cm (13 inch) pieces from 2.5 by 20 cm (1 by 8 inch) board.

  2. 2

    Set the angle on your table saw to 22.5 degrees off centre to the right. Because your saw blade is normally 90 degrees, this will give you a 67.5 degree cut.

  3. 3

    Place the 32.5 cm (13 inch) board flat on the table. Measure 1.2 cm (1/2 inch) from the short edge of board and draw a cut line across the board. Repeat for the other side. Cut the angled cut, along the marked cut line, from the right side of the board on your table saw.

  4. 4

    Leaving the board flat on the table, swing it around and cut the other edge along the cut line. You will now have a 30 cm (12 inch) board with two 67.4 degree outward angles. Repeat for the other seven boards.

  5. 5

    Assemble your octagon by placing each board on its long edge with the short side to the inside. Spread wood glue along each edge and press the edges together. After all the pieces are glued in place, wrap the web clamp around the piece to hold it securely.

  6. 6

    Place the octagon on top of the plywood after the glue has dried. Mark around the outside edge of the octagon on the plywood. If you want a lid, mark two of these pieces. Cut the bottom piece out using the table saw.

  7. 7

    Apply wood glue along the perimeter of the inside face of the plywood. Place the bottom piece on top of your box and align all the sides and corners. Your web clamp should still be in place. Screw the plywood onto the bottom of the octagon sides.

  8. 8

    Nail the octagon sides together using 1.8 cm (3/4 inch) finishing nails.

Tips and warnings

  • You can make any number of sides by the formula 180(n-2)/2n = angle of each mitred cut.
  • If you make a taller box, use two web clamps, one at the top and one at the bottom.
  • You can secure the lid by placing it under the octagon sides before you put the bottom on. Then glue 15 cm (6 inch) pieces of scrap wood to the lid up against two opposite edges. This will prevent the lid from sliding off while still allowing easy removal.

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