How to Make a Fake Rock Mountain

A fake rock mountain adds a decorative touch to a realistic scene for a reptile enclosure, a diorama, a marketing scene, a school project or other various craft endeavours. Building a mountain of fake rock makes it portable---with some adult assistance, this is a suitable craft project for children. Reuse packing materials to make this a green recycling project. With hobby tools and inexpensive supplies, you can make a fake rock mountain in one day.

Cut chunks of styrofoam for the fake rock mountain using a utility knife. Make the chunks narrow or pointed at the top and wide at the bottom to create the mountain's top. Depending on the sizes of the styrofoam pieces, you may need to build the mountain in two or three tiers.

Create thicker pieces of styrofoam for the lower level of the mountain, if a taller mountain is desired. Cut wedges of styrofoam as thick as possible to make the middle of the mountain wider than the top.

Use the widest pieces of styrofoam for the base of the fake rock mountain. For example, if you're using large bands of styrofoam that protected a computer or other electronic item during shipping, set the styrofoam down flat and cut sections of it to fit together for the mountain's base. Make cuts at 30- to 45-degree angles to help form curves.

Assemble the pieces into a mountain shape. Put them together dry, like building blocks. Trim them where needed, for example, to make the tip of the mountain more pointed.

Cut 1 to 2 inch wedges into the sides of the mountain to give it a craggy appearance. Extend the cuts carefully through each tier of the mountain.

Apply glue to the side edges of two of the mountain top pieces. Press them together firmly and hold for a count of 30. Repeat with each piece of the top tier to form the mountain peak.

Glue the pieces of the middle tier of the mountain together so that each edge attaches to the piece next to it. Apply glue to the top of the middle tier and place the fake mountain top on the middle tier. Press the mountain top down carefully and hold it for a count of 30.

Glue the bottom tier of the fake rock mountain together the same way as the top two tiers. Spread glue on the top of the bottom tier. Press the rest of the mountain down on the base of the fake mountain. Adjust it so it's centred and the crags you cut line up. Hold it for 30 seconds.

Prep to spray paint the mountain. Open the windows or spray paint outdoors. Shake the granite spray paint for 15 seconds.

Spray the paint on the fake rock mountain in a 1-foot sweeping motion. Keep your arm moving as you spray to coat the fake rock mountain evenly. Alternatively, spray patches of colour of two or more earth colours on the fake rock mountain, such as grey, tan and brown to give it a dappled, natural rock appearance.


Change the blade of the utility knife if it loses sharpness.


Keep your fingers away from the blade of the utility knife at all times.

Things You'll Need

  • Picture of a mountain for a model
  • Utility knife
  • Large pieces of styrofoam packaging material
  • Craft glue
  • Granite spray paint (or other colour paints depending on the scene you want)
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About the Author

Gryphon Adams began publishing in 1985. He contributed to the "San Francisco Chronicle" and "Dark Voices." Adams writes about a variety of topics, including teaching, floral design, landscaping and home furnishings. Adams is a certified health educator and a massage practitioner. He received his Master of Fine Arts at San Francisco State University.