Create a beautiful concrete countertop (© Sunset)

Inexpensive and strong, concrete holds up houses, paves driveways and keeps fence posts from tipping over.

But beyond these utilitarian roles, it also excels as a decorative material, which is why it's showing up in more and more houses in everything from countertops and fireplace surrounds to tabletops and garden art.

This project features a cast-in-place countertop with an optional terrazzo finish flecked with bits of white marble, mother-of-pearl and cobalt-blue glass. Casting the countertop in place lets you skip both the heavy lifting and the "upside down and backward" thinking involved in pre-casting into a mirror-image mold. But troweling the surface smooth does require skill. Practice on other projects first.

The countertop rests on a base of ½-inch-thick cement board, enabling you to keep the concrete 1 inch thick except at the edges, which are just deep enough to hide the cement board. The result is a normal-height countertop that's easily supported by standard cabinets. Reinforcing consists of galvanized-steel stucco lath, so you must use aggregate small enough to fit through the openings. We used Buddy Rhodes Concrete Counter Mix, which contains white cement and bits of white marble, but a standard sand mix would be fine. We troweled blue recycled glass and a few handfuls of mother-of-pearl into the surface and sanded it a few days later by hand, because a polishing machine would have made a mess in the room.

Directions

Outline shape of countertop (© Sunset)

1. Make a template by outlining the shape of your countertop on cardboard. The edges should be flush with the sides of the cabinet. If the counter is bigger than a sheet of cement board, mark the joints on the template; they must be placed over the cabinet walls so the board is supported from below. Mark the sink outline using the template packaged with it.

You can also use the sink template to create a plug out of foam insulation that's at least 1½ inches thick. This will keep the sink free of concrete. A jigsaw or band saw works well to cut foam. Sand the edges of the foam and wrap them with plastic tape so they are smooth. If you see gaps that you don't like, fill them with a paste of cement and water. Allow them to harden for a few days. Polish with wet-dry sandpaper. Seal and wax the counter before you use it.

Cut cement board to fit (© Sunset)

2. Cut the cement board to fit. For straight cuts, score a line with a utility knife or a knife made for cement board. Snap the sides into a fold and cut through the board's interior mesh, as shown.

Cut hole with jigsaw tool (© Sunset)

3. Cut a hole for the sink and other curves with a jigsaw fitted with a wood blade. The blade will wear out fast; have a spare.


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Cover seams with adhesive mesh tape (© Sunset)

4. Drape plastic over the cabinets and against the backsplash. Clamp 2-by-4s along the top of the cabinets to support the plastic molding that will form the countertop's outside edge; place wooden molding of equal height along the backsplash. Then set the cement board in place so that it butts against the backsplash molding. Secure the foam plug in place with pieces of scrap wood from below. To guard against cracks appearing in the countertop, cover seams in the cement board with the adhesive mesh tape.

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Dampen cement board with water (© Sunset)

5. With tin snips, cut 2½-pound galvanized-steel stucco mesh to match the countertop, minus a 1-inch gap along all edges, including around the sink. If you need multiple pieces, overlap the mesh by a few inches. Before you mix the concrete, dampen the cement board with water. If the cement board dries out, repeat this step just before you fill the form, but blot up any puddles.