How to Make a Styrofoam Boulder

Lone tree and boulder image by peejay from

Things You'll Need

  • Large Styrofoam cube
  • Hobby knife
  • Candle wax (optional)
  • Safety goggles
  • Acrylic-based spray paint (grey, brown, black)
  • Artificial moss
  • Spray-on glue
  • Gloves (optional)

Nature props in theatrical productions and on movie sets create the appearance of an outdoor scene. Styrofoam is often chosen due to its light weight and transportability. Shape or paint Styrofoam to look like nearly anything--a tree, shrubbery, or even an animal. A large moss-covered boulder will add a touch of convincing realism to your child's upcoming "outdoor" play. Don't worry about excess preparation--this is a quick project that can be finished in an afternoon.

Cut the boulder to shape by slicing off all corners of the Styrofoam with a sharp hobby knife. Round the edges of the cube and cut a few gouges here and there for a more realistic appearance. For smoother cuts, lubricate the knife blade with candle wax.

Put on your safety goggles. If your child is helping you paint the boulder, ensure that they wear goggles as well.

Hold the can of acrylic-based paint about six inches from the Styrofoam and spray on a grey base coat. Cover the entire boulder with grey paint.

Add depth to the boulder by spraying a light coat of black paint in the gouges you made on the Styrofoam. Spray brown patches near the bottom of the Styrofoam to suggest dried dirt. Allow all paint to dry for one hour or more.

Grab several clumps of artificial moss and affix them to the top and sides of the boulder using spray-on glue. Avoid sticky hands by using gloves during this step. Allow the glue to set and harden for one hour or more.


  • All of the materials required for this project can be found at your local hobby or craft supply store.


  • If your child is helping you with this craft project, reserve the hobby knife cutting for yourself. Additionally, supervise the use of any paint or glue product.