Styrofoam Cardboard Crumpled newspaper Plywood Expanding foam

A hot wire foam cutter works well to shape styrofoam. If you’re using plywood or cardboard, cut small squares and then stack them on top of each other to create a rock shape. Then, use a saw to cut off the hard edges and smooth them out. To make a rock out of expanding foam, spray the foam into a circular pile, then wait for it to harden. Use a saw to shave down the sides and smooth the foam into a rock shape.

Use wire twist ties to secure the wire frame to your rock base.

You can reduce the sand, and add 1 part peat moss to create a more porous artificial rock. [5] X Research source If you want to use the fake rocks in an area exposed to water, use a hydraulic cement mix instead.

Stir the mortar mix into the water as you add it. Watch closely as you add mortar so your mixture does not get too thick. Aim for a cookie dough-like consistency.

Ensure the mixture is fully mixed and uniformly wet. Add more water if necessary to get the consistency of a thick paste. You do not want the mixture to be runny. Unmixed blobs of sand will cause weak spots in the finished rock; be sure to mix everything completely.

You can also use your hands to push and spread the mortar mix around. Just be sure to wear rubber gloves to protect your skin. You can cover the bottom of the rock with mortar mix, or you can leave it as-is. If your rock is going to be sitting on the ground, don’t worry about spreading the mixture to the very bottom.

Use your trowel to create dips and creases in the surface of the mortar. Press a real rock into the mortar to make imprints of the rock’s texture. Press a sea sponge or scouring pad into the rock to create a pock marked look. Wrap a plastic bag around your hand and press it into the mortar to give a wrinkled look.

Although 75% of the curing is completed after 1 week, it may take up to a month for cement to cure completely. However, the outside of the rock will be dry after 3 to 5 days.

Make sure the outside of the rock is fully dry before you try brushing it. Otherwise, it could crumble.

Painting is totally optional, but many people find that it makes large rocks look more realistic.

Use small rocks to create a pathway or line a firepit. Use bigger rocks to cover up septic tank hatches or electrical boxes.