The side strips or side pieces for the mold are cut from a sheet of laminate covered MDF.

Step 1:

Measure one of the sides and cut a piece of side strip to that length. The side strip in our example is 3 1/4 inches high. (3/4 inch for the laminate covered MDF and 2 1/2 inches for the depth of the concrete).

Step 2:

Line up the side piece against the base and mark the spot for the kerf for the aluminum divider. Cut the kerf in the side piece approximately 3/16 inch deep.

Step 3:

Apply a layer of silicone caulk to the edge of the base where that side strip will go.

Step 4:

Line up the side piece, clamp it into position using pipe, bar and/or C clamps. Drill pilot holes and use the countersink bit. Screw the side piece to the base of the mold every 6 inches. The side strip sits on the top of the workbench, not on the top of the base of the mold.

Step 5:

Repeat Steps 2 through 4 for the opposite side.

Step 6:

Measure the width of an end, including the side pieces and cut a length of side strip to that size.

Step 7:

Apply some silicone caulk to the edge of the base and the ends of the side strips.

Step 8:

Line up the end piece, clamp it into position using pipe, bar and/or C clamps. Drill pilot holes and use the countersink bit. Screw the end piece to the base of the mold every 6 inches and to the ends of the side strips. The end strip sits on the top of the workbench, not on the top of the mold base.

Step 9:

Repeat Steps 6 through 8 on the other end.

Step 10:

Apply a bead of silicone caulk on the inside edge between the base and the side and end pieces. Smooth with your finger or a caulk bead tool to create a concave finish, as shown in Figure 13.

Step 11:

Measure the outside sides including the end pieces and cut laminate strips about 1 inch shorter than the side pieces. In our example this would be 2 1/2 inches.

Step 12:

Screw the pieces to the side piece already mounted. Screw from the outside towards the mold. You do not want any screw heads on the inside of the mold. Use a pilot hole and countersink bit.

Note: When you drill the pilot holes for these screws do not allow the drill to go through the side piece and into the mold; the area where you will pour the concrete.

Step 13:

Repeat Steps 11 and 12 for the end pieces.

Step 14:

Cover the screw heads with modeling clay.

Step 15:

Cut laminate strips approximately 2 1/2 inches wide that will sit flat on the workbench and tight against the second outside laminate strips that you installed in Steps 11 through 13. It is best to use bar or pipe clamps to draw them tight.

Step 16:

Drill pilot holes, use the countersink bit and screw these pieces, every 6 inches, directly to the workbench using 2 inch drywall screws. These pieces of laminate covered MDF should be tight up against the second side and end support that was previously installed.

Step 17:

Cover the screw heads with modeling clay.

Continued - How to make the mold frame for the sink in your concrete countertop

How to Make Concrete Countertops - Index