How to Make Lightweight Concrete Structures

Cut a plywood base to the necessary shape for the bottom of the concrete structure.

Build an armature out of boards to create a “skeleton” of the structure. Screw boards together in the necessary formation. Attach the bottom of the armature to the plywood base with screws.

Form wire mesh around the armature to shape the “body” or the structure. Bend and mold the wire mesh by hand, cutting it where necessary with wire cutters and attaching ends by twisting opposing wires together.

Spray the entire structure with a layer of spray foam. Allow the foam to set up.

Carve the foam to hone the contours of the form. Appropriate tools for carving foam include surface-forming tools, files, rasps, hacksaws, hot wire cutters, carving knives and sandpaper.

Add enough water to concrete mix to make a slightly soupy consistency. Dip strips of burlap in the wet concrete. Cover the foam form with the dipped strips. Apply the strips in various, overlapping directions.

Create another batch of concrete, this time with a thicker, paste-like consistency. Add concrete pigment if color is desired. Cover the burlap layer with a 3/4-inch coat of the thick concrete, applying the concrete with a trowel. Smooth the surface with the trowel.

Stain the cured concrete with concrete stain, if color is desired, then coat the concrete with concrete sealer, using a paintbrush.