How to Make Fake Rocks

Written by michelle diane
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That space in the backyard would be perfect for your garden if not for that ugly septic piping. Visions of hummingbirds and stylish soirées dance in your head. You can almost smell the lilacs and gladiolas, but hideous hardware haunts your daydreams. You cannot relocate the pipe; you can conceal the dreadful thing with a fake rock garden. Best of all, in just a few hours, you can make the artificial stones yourself.

Skill level:

Things you need

  • Styrofoam
  • Tin snips
  • Pliers
  • Tie wire
  • Gloves
  • Razor knife
  • Safety glasses
  • Chicken wire
  • Steel mesh
  • Point trowel
  • Sea sponge
  • Scraping stone
  • Stiff brush
  • Paint
  • Spray bottles
  • Concrete sealant

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  1. 1

    Cut and stack Styrofoam pieces to create the desired bulk and shape of your fake rock. Bend a piece of tie wire so there is a 90-degree hook in one end. Penetrate all layers with the other end. The hook should be flush with the top layer. Friction will cause it to grasp and hold the foam layers together.

  2. 2

    Contour your rock by cutting pieces off the original foam form. You can also attach custom-cut pieces of foam around the sides to produce a natural sloping effect.

  3. 3

    Wrap the Styrofoam form loosely in steel mesh. Use small pieces of foam for spacers. This allows the steel mesh to be completely encased by the concrete, strengthening your artificial rock and protecting it against hairline fractures.

  4. 4

    Secure the steel mesh to your form using the same type wire pins you made to hold the foam layers together. Ensure the steel form is solid enough to not shake or slip when you pour the concrete. Bend any protruding wires into the foam.

  5. 5

    Tightly wrap your fake rock form in several layers of chicken wire with more layers on vertical sides. Use pliers to bend the chicken wire and attach it to the steel mesh.

  1. 1

    Mix your concrete, according to manufacturer’s directions, to a strength of 50 to 75 MPa.

  2. 2

    Apply concrete to your fake rock a handful at a time. Build from base to top. Work quickly to thoroughly cover the entire frame in concrete to allow time to sculpt your rock.

  3. 3

    Study rock formations. Simulate them on your artificial rock using a point trowel for sculpting and sea sponge for texturing.

  4. 4

    Allow the concrete to cure for at least 3 days.

  1. 1

    Smooth the jagged edges from your fake rock with a scraping stone. Work patiently over the entire surface until your artificial rock is as smooth as real stone.

  2. 2

    Wash your rock. Use a stiff brush to remove all the concrete dust, and let it dry completely before painting.

  3. 3

    Mix complementary colors of water-based paint in spray bottles. Mist several layers of paint onto your fake rock until you achieve the desired effect. Allow to dry between coats.

  4. 4

    Seal and protect your fake rock with a water-based concrete sealant. Apply three layers. Let one layer dry completely before applying the next. Reapply annually.

Tips and warnings

  • Construct your Styrofoam form approximately 3 inches in diameter smaller than you want your finished product. Remember, you’ll be covering it with concrete.
  • The final product is not intended to be load bearing and does not possess the structural integrity to be used for such purposes.
  • Wear a mask when working with concrete to avoid inhaling dangerous dust and fibers.
  • Always wear gloves and goggles to protect yourself from injury.

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