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How to Make Concrete Countertops


How to remove the concrete countertop from its mold

Step 1:

Remove all of the screws that hold the concrete countertop mold to the workbench. Check the quantity of screws that you have removed from the quantity that you wrote down when you installed them. Hopefully the numbers are the same. If you have not removed them all, keep searching until you find the screws that are still in place.

Note: Some of the screws, holding the mold to the workbench, will be in the area that provides the hole for the sink!

Note: The scew heads were covered with modeling clay so that they would not be covered in concrete during the pour.

Step 2:

Remove the screws holding the backer boards to the mold sides, both along the outside of the mold and in the sink hole location.

Step 3:

Remove the screws holding the end pieces to the side pieces and the screws that hold the end and side pieces to the base.

Step 4:

At this point there should be no screws holding any of the side and end pieces on the outside of the mold. Survey the mold and make sure all of the screws have actually been removed.

12 inch pry bar

Figure G - 12" pry bar

Place the sharp edge of a small pry bar, as shown in Figure G, between an end joint and a side. Do not go past the thickness of the laminate covered MDF, 3/4 of an inch and pry the two pieces apart. Once you have the pieces separated, it should have only been the silicone caulk holding them together, pull the side piece away from the mold. If you have a problem in breaking the seal between the laminate on the MDF and the concrete place a wood or plastic wedge, as shown in Figure H, between the concrete and the laminate, at the farthest point that has separated. Tapping on the top of the wedge with a wood or rubber mallet should force the wedge to break the seal between the two materials.

Plastic wedge

Figure H - Plastic wedge

Once the sides are removed you can remove the ends of the mold by tapping on the end boards with a wood or rubber mallet. If they do not release easily, slide a wood or plastic wedge into the gap between the concrete and the side board towards one end of the end piece and tap on the top of the wedge with the mallet.

Note: On rare occasions a side or end piece refuses to release from the laminate. If this should occur you can try using the wood or plastic wedge between the laminate and the concrete and then use the pry bar as a lever between the wood wedge and laminate covered MDF.

Warning: Never apply leverage directly against the concrete. Apply the leverage towards the mold.

Step 5:

With all of the backer boards removed from the sink hole location you will need to remove the sides of the sink hole. This can be a tricky process as the boards were compressed very tightly by the concrete when it was poured.

Identify which boards are free at the corners and work to pry them free first. Use the wood or plastic wedge, mallet and pry bar as necessary. If you do not succeed with the wedge, mallet and pry bar your only real alternative is to cut the laminate covered MDF. Use a sharp chisel and keep it away from the concrete at least an 1/8 of an inch and drive the chisel down and through a side piece. Once the pressure is released on the first piece and it is removed the others should come out relatively easily.

Step 6:

Remove the long screw that is holding the mushroom spacer in position. In most cases the large plywood pieces will be loose and should be easy to remove. If they do not come out easily, insert a screw into the MDF leaving the head exposed and use a pry bar to pull on the screw and hence release the large pieces of MDF. It may take two steps, release the first one and then do the same to release the second one.

Note: Do not try to remove the PVC pipe at this point. It will be removed once the bottom of the mold is removed and the concrete countertop is placed in its final position.

Step 7:

The edges of the concrete are quite sharp and need to be eased somewhat. This is best accomplished by using a 400 grit diamond sanding pad. Ease the outside edges and the edges for the sink hole. Easing the edges helps prevent them from chipping as you flip the concrete countertop and it is safer for the hands of those doing the flipping!

Step 8:

Note: Our example countertop was divided into two sections, but to remove the base of the mold, the entire mold, the two sections, must be flipped over as one complete unit. You will need the help of a few "strong" friends to accomplish this.

Place a layer of 1 inch rigid foam on the top of the entire concrete countertop, cut to size and tape it with masking tape to the edges of the concrete countertop. Leave or make a hole large enough for the spacer for the faucet and/or other accessories to be driven out of the concrete.

Slide the concrete countertop and its base towards the edge of the workbench so that almost half of the countertop is hanging off the edge of the workbench. Lift the concrete up and stand it on its edge and then allow it to go slowly forward (with your friends standing on the other side and supporting the concrete countertop as it is slowlylowered) so that it rests on top of the rigid foam.

Note: When flipping the concrete countertop over do not allow it to flex as this will most likely cause the countertop to crack. (This is why you need a number of people to maneuver the weight of the countertop)

Note: Remember that the base of the mold is not "fastened" to the piece of concrete, so when you flip it over, you must hold on to both the base and the concrete.

Slide the concrete so that it is in the center of the workbench with the laminated MDF facing up.

Once the concrete countertop has been flipped over you can remove the laminated MDF base. In many cases the base will have come loose as you are flipping it. If the base is stubborn, which does happen, insert wood or plastic shims between the base and the concrete and tap on the heads of the shims with a wood or rubber mallet. In exceptional cases it may be necessary to insert shims all the way around the mold to get the base to release.

Step 9:

Remove the aluminum pieces that separated the concrete countertop into two pieces.

Step 10:

Once you have released the base, slide the countertop so that the mushroom spacers, for the faucets and/or accessories, are over the edge of the workbench. Using a piece of wood dowel the size of the PVC pipe and a mallet, drive the PVC pipe from the concrete countertop. The PVC pipe should release itself quite easily.

After you have removed all remnants of the mold, return it to the center of the workbench.

Continued - How to Finish Concrete Countertops

How to Make Concrete Countertops - Index