In this DIY concrete countertop tutorial, I'm going to walk you though the process of creating the form, pouring, and polishing your very own. For our concrete kitchen countertop, we used Butterfield Colour mix, with Surecrete Concrete Countertop Sealer.

The first thing to understand about concrete is it’s not all created equal. There are various ways to mix concrete that will effect porosity and strength.

Traditional Concrete Countertop Mix
If you use a traditional sand, gravel, water mix you will have a high porosity low strength concrete (3000 psi compressive strength) concrete countertop. This type of countertop will be supportable to staining, cracking and will need to be poured thicker to maintain strength ( at least 1.5″ thick). This is by far the cheapest way to make your own countertop at just .50 cents a square ft for materials and it may look great for a year or two. With constant use ketchup, wine, blueberries and many other products will stain the counter. So whats the solution ?

Polymer modified Counter Top Mix
A glass fiber reinforced, polymer modified, self-consolidating mix with a 28-day compressive strength of approximately 11,000 psi. This mix doesn’t use water so it eliminates the air pockets left behind when water evaporates from the traditional concrete mix mentioned above. There are many brands on the market your best to contact your local supplier and see which brand they stock. I used Flat out countertop mix from Butterfeild.

Supplies

diamond cup wheel: https://amzn.to/2MNZBl8
dismond polishing pads: https://amzn.to/2LgerxH
countertop sealer: https://www.surecretedesign.com/product/concrete-c...

Step 1: MAKE THE MOLD

The first thing we need is a sheet of 3/4 “ melamine to make our forms. Cut out a piece that is the exact size you want your counter top to be. It should fit perfectly snug on all edges and make sure to include 1” for a standard overhang.

Next we need to create the sides of our form. Since the base of the form is exactly the size of our countertop, the sides need to be attached to the outside, not on top. To make our countertop depth an 1 1/2” our sides needs to be 2 1/4” wide.

Now we need to put our form together by screwing the sides to the base. And don’t forget to pre-drill your holes to prevent splitting. We also put two air nails in each corner to ensure there are no gaps.

We need to make sure there is no dust or residue on the form. First I vacuumed it and then I cleaned it with paint thinner (you could also use acetone or dish soap).

We’re applying caulking to seal the form but more so to create rounded edges, but before we caulk the seams, we’re applying wax so that we can easily peal away the access caulking.

Now were ready to caulk all the seams including the corner seams. After you apply the caulking you need to shape it right away be fore it gets too sticky or dry. We used a metal ball that was designed to create perfect radius corners simply by running the tool over the silicone.

When its dry you simply peel up the excess silicone.

Step 2: POUR

Now before we start pouring, it is extremely important that you’re working on a perfectly level surface.

We used flat out countertop mix by Butterfield colour mixed w liquid polymer. This countertop mix is glassfiber reinforced, polymer modified, self consolidating, and holds a compressive strength of 11,000 psi. We chose this over reg concrete because its much less porous and therefore much less stain resistant and is 3 times stronger which allows us to pour a thinner slab. If your using traditional concrete mix 1 part portland cement, 2 parts sand, 2 parts pea gravel or 1/4 ” crush washed gravel. If your using a polymer modified mix use instructions on bag.

To eliminate bubbles and create a more flawless finish we are going to use a texturizing gun to spray our first 2 coats. To do this you will needs to sift out the stones and fiberglass from your concrete powder. Now its time to pour the rest of the form you do not needs to sift through the mix for this part. Simply mix the flat out mix with the liquid poly until desired consistency is achieves. It should be similar to the consistency of oatmeal.

If you're using polymer modified concrete you can make your mold as thin as 3/4″ thick (like we did). If your using traditional concrete mix you will need to make it a minimum of 1.5″ thick. We poured ours 3/4" thick and then used a 3/4" spacer to make lighter. In order to lighten the weight of the slab a little but, we going to use a Styrofoam spacer that is 3/4 of a. Inch thick so we only need to pour the mix 3/4 of an inch thick.

Use your fingers to agitate and shake the mix to release any air bubbles. Now place your 3/4 inch pieces of styrofoam in the middle of the mold, leaving about 2” around the outside. The styrofoam should be flush with the top of the mold.

Next were going to screw down the foam to prevent it from floating when we pour the edges. Now pour the edges and adjutant again with your fingers.

Be careful not to overfill the form or you’ll have to sand it down which risks damaging the edges.

Let mold sit for 48 hours with traditional mix or as little as 3 hrs with polymer modified mix.

Step 3: DE-MOLD

Once the concretes set, take off the strapping on top and remove the screws that are holding the mold together, and pry away the melamine pice by piece.Leaving the styrofoam in place, smooth out the bottom edges using a diamond cup wheel.Now flip it over and pry off the top for the grand reveal.

Step 4: FILL PINHOLES

Your piece is going to have some pinholes and other imperfections but were going to fill them in with surecretes XS slurs.First add water to the surface and gently sand with a 200 grinding standing pad. Pour on the slurry and massage in to the concrete with your fingers.then with a trowel, gently remove any excess slurry.

Step 5: POLISH

Now were going to polish our piece using 400 to 800 grit polishing pads. We are wet sanding top prevent scratches in the surface and also eliminate dust.

We didn’t want much aggregate showing so we did a very light sand. Polishing can be a short or long process depending on what you want your finish to look like. If your after a flat look with limited aggregate exposed. You’ll want to wet sand lightly with 200 then 400 grit diamond sanding discs. If your looking for a high shine finish you’ll want to wet sand starting with 200 grit , then 400, 800 and finally 1000 grit diamond sanding discs. You may also need a diamond cup grinding wheel to remove any heavy deposits of concrete on the back side of the countertop pour.

We also used 400 grit wet sanding pads on the edges and sides or to spot sand.

Once you’re done sanding and you’re happy with your finish, you need to thoroughly clean your surface using just a cloth and water.

Step 6: SEAL

This is probably the most important step. Use a high quality sealer specifically designed for counter tops. I used Surecrete concrete countertop sealer but there are many other good products out there. So do some research online and see what else you can find. One recommendation I would give when looking for a good sealer is make use it is a two part sealer. These tend to be far more durable.