Hollow artificial rocks are a nice addition to landscaping and can serve as a cover for unsightly utility boxes. Simple to make, artificial rocks are a good alternative to hauling in large boulders. The artificial rocks are easier to move and do not require heavy equipment to put them in place. Shaped to fit specific locations or needs, artificial rocks are a landscaping addition that looks natural, but is hand made to fit your needs.
Shape the cardboard box or styrofoam block by cutting away corners and rounding the appearance. Styrofoam can be cut with a utility knife using care to keep from cutting your hands. Cardboard can be cut with a utility knife or flattened in to create the desired shape. If you are making your rock a particular size or shape to cover a utility box or other unsightly feature, be sure the box or block you use fits this and you do not cut away too much in the shaping.
Cover the form with chicken wire or wire mesh, using the tin snips to clip the piece to size. Wearing the leather gloves, shape the chicken wire or mesh over the cardboard or styrofoam until it begins to get the desired rock like shape. This is the base of your rock.
Mix the Portland cement with water a little at a time until you get a thick semi dry consistency something like dough. It should be moldable by hand. Add sand to increase the grain and add texture, making sure to add more water if it drys the mix too much. Using your leather gloves and trowel, begin at the bottom of your rock mold and begin layering the mixture over the form working from the bottom up. When a layer of the mix has covered the entire form, let dry.
Prepare the pre-mixed concrete according to the directions. Layer this over the top of the dried rock using the trowel. Add little nicks or bumps to give it a realistic look as you layer the concrete over the form. Allow to dry. If a styrofoam block was used as a form, now is the time to hollow the rock. Carefully cut away the styrofoam from the inside of the rock using the utility knife, and remove the pieces. Some styrofoam can be left if a particular size hollow is desired.
Choose a stain or concrete dye if color variation is preferred. Apply the stain or dye to make a natural rock-like finish. Let dry. Seal the rock with concrete sealant whether or not stain is used. Once dried, the rock can be placed in the landscape.