DIY Concrete Countertops

Build a form for the countertop out of melamine. This is plywood that is covered with plastic that prevents concrete from sticking to it. Cut the bottom of the form to meet the countertop's length and width and strips for the side that match the width needed to accommodate the thickness of the countertop plus the thickness of the bottom of the form. Nail the strips to the sides of the bottom panel.

Trace the outline of the template for the new sink onto a piece of 1 1/2-inch thick foam board insulation. The sink manufacturer should provide the template with the sink.

Cut the insulation board along the trace lines and remove the sink template using a jigsaw.

Create template out of insulation board for the faucet and sink handles by driving a 1 1/2-inch pipe into the insulation board. Do not use the piece you cut for the sink template for this.

Place clear packing tape onto the pieces of foam you cut out for the templates except for the sides of the foam pieces that you will attach to the melamine form. The packing tape prevents the concrete from sticking to the foam.

Set the foam pieces into the correct position in the bottom of the melamine form, using silicone caulk to attach the foam to the melamine.

Apply silicone caulk to the inner corners of the melamine board to round the edges of the countertop. Apply caulk-shaping spray to the caulk and smooth it with your fingers.

Prepare a batch of concrete, following the manufacturer's instructions. Add pigment to the mix and stir it thoroughly to color the countertop.

Pour the concrete into the form, filling it about two-thirds of the way. Vibrate the form to remove trapped air bubbles by holding an orbital sander underneath the form.

Lay wire mesh or rebar on top of the concrete except where the foam pieces are located.

Run the orbital sander against the bottom of the form again until the wire mesh or rebar sinks into the concrete, then fill the rest of the form.

Smooth the surface of the concrete by dragging a 2-by-4 board across the top of the form. Allow the concrete to cure for about a week.

Remove the countertop from the form.

Apply concrete sealant to the countertop to protect it from staining.