[Feb 2016 Update: If you want to add an integral sink to your countertop, make sure to also check out the tutorial on how to make a concrete counter or vanity with integral sink. Here’s the one I made…]
Now back to our regularly scheduled program…
In the last post, Part 1 – Intro & Templating, we worked on creating the template for building the form that will give your countertop it’s shape. Now, we will actually be building the form.
The form is built from melamine board. Melamine is basically particle board covered with a white melamine sheath. You’ll often see it used for shelving. It comes in various sizes and can be purchased at most home improvement stores.
We used two large 48″ x 96″ (3/4″ thick) melamine boards to configure our form, but of course, adjust for the size you are building.
Use clamps to secure your template to your board. To make this as easy as possible, align the back edge of your countertop template to the straight edge of the board. You can see how we did that on the left side of the image above.
Use a pencil to trace along the inside and outside of your template. Tracing along all the interior edges will simply help you stay oriented on the board once the template is removed. If you’ll be using decorative edges on the front and sides of your countertop, add that additional width to the edges where the decorative edges will be placed, i.e, if your edge mold is 1″ thick, add one inch to the sides that will accommodate the molds.
Next, X-out all the open spaces on the board. This is simply another tip for staying oriented. It will tell us that the X-out surface will face down when pouring the concrete. Why? Because when we pour the concrete, the surface we pour it on will end up being the top surface of the countertop. Therefore, you’ll be pouring a mirror image of the template, so we turn over the board.
Use a skil saw (or other electric saw) to cut the outside edges of your marked form. Be as accurate as possible (obviously).
Place your template over the cut out form to double check for accuracy.
In the photo below, on the left side, you can see how we left extra space for our edge molds.
On the far end of the image above, we wanted a rounded side to create a space for bar seating on that end of the countertop. So we used a bent piece of plywood strip to outline a gentle radius on that end of the countertop and then cut.
As mentioned earlier, we built this countertop in two pieces. So, next, we will create the joint where the two pieces will connect. In the image above, we used two melamine boards to create this form. You can see in the middle of the photo where one board over laps the other.
If you are using two boards to create your form, then with your boards overlapping, use your template to make sure everything is aligned to the template and then reclamp the two boards together.
Your joint doesn’t need to be straight. We decided our joint would mimic a marble vein, and drew it on with pencil.
Notice that the joint overlaps the doubled boards. We will be using the bottom board as the second part of our countertop form.
Use a jigsaw to cut through the doubled boards.
When you remove the cut piece in the image above, the two parts of the countertop should fit together perfectly.
Notice no writing on the melanine? That’s because we also flipped the board. Remember, we’re pouring the concrete on a mirror image of the countertop. So the writing is now on the side facing down.
Now, it’s time to create the form edges. First, we’ll create the mold edge for the joint (you know, that crooked part that we cut to mimic a marble vein).
If your joint is going to have a straight edge, you can skip this step and simply use the 2 ¾” melamine strips that we’ll discuss below. But if you are making a crooked joint then read on..
Use roofing paper to form the crooked joint edge. Why roofing paper? Simply because it’s a heavy material that can be easily formed and hold it’s shape.
Cut a strip of the roofing paper 2 ¾” wide.
Crinkle up the roofing paper to give it a more natural stone-like finish (since we’re mimicking a marble finish).
Slide your crinkled roofing paper into your vein joint and press the two sides of the countertop form together to hold it in place.
Now, we’re ready to install the external edges.
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