How to Build Cement Rocks and Boulders

Cement rocks can be large or small

There are several ways you can build cement rocks and boulders. Here are three methods that will create realistic rocks you can use for decoration or landscaping.

Instructions

1. 

   You can make a hollow fake rock or boulder with cement. This is ideal if you want to use it to hide something beneath or if you want to create a large chunk of rock that can be entered, like a cave or a pet house.

2. 

   Hollow rocks are made by building a framework of wood or bent metal like rebar. Cover the framework with a fine mesh like hardware cloth or small gauge chicken wire. Shape this in the form your want for your rock and attach pieces together with twisted wire.

3. 

   Once you have your finished framework, you can apply a coating of cement. The cement should be a mixture of Portland cement, sand and water and should be quite thick so it adheres to the framework. I like to incorporate vermiculite (which gives it some mica glitter) or perlite to make the cement mixture a little lighter. You may need to apply several layers until you are able to cover the rock smoothly.

4. 

   Another way to build a cement rock is to give it a solid core. A solid core rock can be sculpted out of foam rubber or better, styrofoam. Pieces can be cut and glued together until your have the form you want. Cover your lightweight shape with a wire framing -- lots of wire or hardware cloth or similar material -- for the cement to adhere to. Then you can apply your cement to the surface, sculpting to the texture and shape you want.

5. A second way to make a solid core cement rock is to create a mold by casting your own mold make of contractor's sealant over an existing rock, then pouring your concrete (or plaster) inside. Once dry you can remove the mold and paint (and if plaster, seal) your rock. For more information on casting molds or finding fake rock molds, check the additional resources list below.

6. 

   Whether you use a hollow or solid core, the sculpting of the concrete and coloring will be the biggest factor in how realistic your rock appears. Use other rocks in your garden to copy colors. You can spray the paint on in layers or blend it with a brush. Consider adding shadows, veining of colors or dark crack lines for more realism.

7. For more ideas and information on how to build cement rocks and boulders and using them in your landscape, please follow the links under 'Resources'.

Resources

• More on fake rocks
• An article on cement rocks
• Landscaping info and ideas
• Artificial rock and boulder molds