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Build a flower box

  • Difficulty: hammer
    Close Difficulty
    Beginner Do-It-Yourselfer - Easy
    Intermediate Do-It-Yourselfer - Moderate
    Experienced Do-It-Yourselfer - Difficult
    Professional - Expert
  • Completion Time : 1 day

Flower boxes are must-have additions on a treated-wood terrace. They add colour, style and fashion to the look of the home. The model illustrated here features a false bottom lined with polystyrene board and a polyethylene film to support a flower pot and prevent the deterioration of the wood from water. For a professional look the sides can be lined with boards positioned at 45°.

In addition, use treated-wood screws (porcelain coated or stainless steel) to build your flower box, otherwise you'll be faced with traces of rust after a few years.


Tools and materials required


  • Electric drill
  • Gloves
  • Hammer
  • Mitre saw
  • Safety glasses
  • Carpenter’s pencil
  • Straight edge or chalk line



  • Plywood - ½" (5/8" OSB can be used)
  • 2" × 2" x 96" strips of treated lumber*
  • 2" × 4" x 144" boards of treated lumber*
  • 2" × 6" x 96" boards of treated lumber*
  • 1" x 4" x 96" boards of treated lumber*
  • 1 ¼" x 4" x 96" boards of treated lumber*
  • 1"x 6" x 96" boards of treated lumber*
  • (*lengths depend on size of flower box)
  • Polystyrene panel (of the interior, if required) or polystyrene film
  • Construction glue
  • Exterior silicone caulking (if using polystyrene panels
  • Treated wood screws and nails 

Before Assembly

Elevation flower box
If using raw, treated lumber:

  • Heed warnings about using it for a food service area. Once sealed with stain or paint this threat will not be as urgent.
  • Use galvanized hardware and not aluminum as aluminum can corrode when next to the chemicals in wood treatment.
  • Use a wood treatment to seal the cut ends of the boards.
  • Treated boards should be lightly-sanded or pressure-washed beforehand to open the pores and let the stain or paint in or let the coffee table weather for a month or two.

For other types of wood:

  • Stain boards before assembly to prevent warping and moss and mould in the cracks,
  • Use a pressure washer to clean the wood and let dry thoroughly. This will open the pores in the wood to let the stain or paint in.

For this project:

  • We have chosen to use screws to assemble the box. You can also use nails.
  • You can use ½" plywood or 5/8" OSB for the sides.
  • Pressure-treated lumber can be used but must not come into contact with live flowers or plants.
  • Polystyrene film or polystyrene panels, or both, can be used for the box liner. You can also buy plant liners at the garden store.


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