How to Cast a Concrete Counter
Concrete can be used to cast countertops that are organic and earthy-looking. However you can finish freshly-cast concrete in many ways. Leave it looking rough-hewn or grind and polish it to a high sheen. Cast concrete countertops can be given many looks by adding colored pigments and mixing in different materials--such as ground up plastic confetti--to add visual texture. Making your own concrete countertops can greatly reduce the cost of a kitchen countertop installation. Does this Spark an idea?
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Things You'll Need
- Flat work surface
- Carpenter's level
- Pencil
- Luan board or paper
- Tape measure
- Melamine board in 4 by 8-foot sheets
- Table saw
- Electric drill
- 1 1/2 inch wood screws
- Scrolling sabre saw
- Pre-fab knockouts
- Glue
- 3/4 inch re-bar
- Wire mesh
- Hack saw
- Wire
- Wire clippers
- Silicone caulk
- Caulk gun
- Pre-formulated concrete
- Water
- Hoe
- Wheelbarrow
- Rubber mallet
- 1 roll plastic
- Variable speed grinder
- Assorted diamond grinding pads
- Concrete sealer and wax
- Brush
- Buffing pad
Instructions
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1
Select a work area such as a garage with a large, flat work surface that can take a lot of weight.
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2
Make a pattern of the counter top to be cast. Draw the pattern on luan--a thin wood veneer used for the surface of hollow core doors or paper. Mark the location of holes for faucets and sink. Cut out pattern with sabre saw.
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3
Build a mold from the pattern. Use melamine board--chipboard that is coated with polymer resin--trace the pattern on the melamine and cut it out with the sabre saw. Cut out faucet and sink openings. Plug hole openings with pre-fab knockouts--forms that the concrete will flow around--so when the concrete sets up, the knockouts can be removed leaving openings to slide the sink and faucets into. Determine the thickness of the counter top, cut melamine strips on the table saw to that depth and screw the strips to the edges of the base.
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4
Seal the inside of the mold with silicone caulk. Set the carpenter's level inside the mold and level it.
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5
Cut 3/4 inch re-bar (steel rods used to re-enforce concrete) and wire mesh to fit inside the mold. Tie them together with wire as if creating one side of a metal cage. Suspend the re-bar and mesh from wires attached to wood screws inserted into the outside of the mold's walls.
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6
Mix the pre-formulated concrete mix with water in a wheelbarrow with a hoe. Make it the consistency of runny oatmeal. Add the water slowly. Pour the concrete into the mold. Tap the side of the mold with a rubber mallet to force any bubbles to the surface.
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7
Cover the top of the mold with a sheet of plastic so the concrete sets up slowly. Keep out of direct sunlight. It should take about four days to cure.
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8
Remove the the sides of the mold after four days and let cure for three more days.
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9
After the three days flip the concrete and take away the melamine base. Remove the knock-outs.
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10
Use a variable speed grinder with diamond grinding pads to sand down the surface of the concrete counter top. Start with a course pad and step down to finer and finer pads until the surface of the concrete is smooth.
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11
Finish surfacing the counter top with concrete sealer and wax to prevent staining.
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Tips & Warnings
The less water used to mix up the concrete the stronger concrete you will get and the less it will shrink.
Rent a small concrete mixer if you are creating a large countertop. This allows faster mixing and a consistent mix throughout the poured project.
Work on a small countertop project first to get the feel for the materials and the method of casting concrete before tackling a big project.
Pour the cast concrete on a day when the humidity will be above 25 percent. The outside temperature should be between 50 and 90 degrees.
After the countertop is installed it should be waxed once a month and resealed when it appears the concrete is becoming susceptible to staining.
