Things You'll Need
Cans of polyurethane spray
Polyurethane rocks are artificial rocks that are made from special foam. The polyurethane foam is the outer portion of the fake rock. The texture and shape of the rocks can be customized according to individual preferences and needs. Polyurethane rocks are straightforward to make, and you can save money instead of purchasing real rocks. The fake rocks are durable and appear as though they are real.
Flatten and lay out a sheet of chicken wire. Use wire cutters to cut the wire to the desired size. Bend and shape the chicken wire to form the outer shape of the fake rock.
Place pieces of cardboard inside the chicken wire frame to reduce the amount of polyurethane foam spray that will be needed.
Apply thin layers of the polyurethane foam spray over the chicken wire. Shape the foam before it expands and sets (you'll have about three minutes).
Cover the rock in multiple layers of the polyurethane foam spray. Once the foam has set completely, use a paint brush to apply latex paint to the exterior surface of the fake rock. A sponge can be used to add a textured look to the rock's surface.
Spray the entire rock with clear sealer to protect it from the elements. Once the sealer has dried, the rock can be placed outdoors in the desired location.
Use a two-by-four board to add support if the fake rock is being used for a structural purpose.
Wear gloves when handling the foam spray.