Install a Concrete Countertop

Learn how to build a concrete countertop that will support a small fireplace.

Hammer Heads : Episode HHEDS-202 -- More Projects »
PHOTO

The concrete countertop raises the fireplace to a comfortable viewing level and provides a fire-proof base for it.
Materials and Tools:

Quikrete Countertop Mix
3/8" rebar
metal lath
rebar wire ties
4'x 8' sheet of 3/4" melamine particleboard
concrete accelerator
car wax
silicone
2" screws
buffing pad
rags
table saw
grinder with cut-off wheel
linesman pliers
caulking gun
caulk
safety glasses
ear plugs

Cut list for the melamine:

one 2'x5' piece
two pieces, 2' x 3-1/4"
two pieces 61-1/2" x 3-1/4". The 3-1/4" sides will be flush with the sides of the 2'x5' panel to create the 2-1/2" deep form.

PHOTO

Figure A
Steps:

1. The first step in making a concrete countertop is to build a form for the concrete. The bottom of the form will be the top of the countertop. Using melamine particleboard for the form keeps the concrete from adhering to it as it dries.

Our counter top was 5' x 2' x 2-1/2" thick. To ensure a straight edge, use a table saw to cut the melamine according to the cut list above.

2. Fabricate the form (figure A) with 2" screws, pre-drilling with a countersink bit to ensure the particleboard will not split or create a mushroom inside the form. Use silicone in every joint inside the form. The thickness and consistency of the silicone will shape the final edge on the countertop, so make sure it is consistent. Tip: Use black silicone to make it easier to see how even it is during application.

PHOTO

Figure B
3. The lath will reinforce the middle structure of the countertop, and the rebar will provide perimeter strength. Cut the lath with your grinder so it will fit inside the form with 2 inches of empty space around the outside. Place the lath pieces in the form.

4. Next bend the 3/8" rebar to fit on top of the outside edge of the lath. Cut the excess with a grinder (figure B); make sure you to earplugs and safety glasses. Place rebar inside the form. Tie the rebar together using rebar ties and the lineman piers, cross looping the ties around the rebar and lath and twisting the wire tightly until it is secure.

PHOTO

Figure C
5. The rebar must float when the concrete is poured into the form; here's how to do that. Add 1" blocks under the lath (figure C). These will suspend the lath while you screw it into place.

6. Next screw some 1-1/4" screws into the sides of the form 3/8" down from top edge. Tie off the rebar structure to the screws, then take out the 1" blocks. Now the rebar is suspended.

7. Mix the concrete and accelerator in a cement mixer according to the manufacturer's instructions. Start with the dry mix, then add water little by little until the cement has a cookie-dough consistency to it.

PHOTO

Figure D
8. Pour the concrete into the form. Wearing rubber gloves, knead the concrete into the corners. Making sure the mixture is in all parts of the form (figure D).

9. After the form is properly filled, let is sit for 15 minutes. Then remove the screws from the sides and snip the wire off to the concrete with some metal snips. Use a piece of straight metal to screed the excess concrete off the form.

10. Use a sander with no sandpaper on it to vibrate the form. This will loosen the concrete into all the corners better and get rid of air pockets. Let the concrete dry completely.

11. Once the concrete is dry, carefully flip over the form and unscrew all screws. Slowly and carefully break apart the form from the concrete. Buff the new countertop with car wax to the desired shine.

Also in this Episode