This is a great table for anyone that needs something a bit heavier for their patio set up.

It all started when I moved to a part of Colorado that was windier than I was accustomed to. It turns out my patio set was more of a kite than a table. Needles to say, the wind finally won and my patio furniture was nothing more than some bent steel legs and a pile of broken glass...

I knew the only way I would be able to have a table on my patio would be if it weighed enough to not fly away. I always wanted to attempt building a concrete counter top, and this was the perfect project to get my feet wet.

Supplies

You will need:

1 x table base - The one I built can be found here
4 x Quikrete 80 lb. Commercial Grade Countertop Mix - Link
1 x Porter cement mix or Similar (used for grouting and filling small holes)
1 x Rebar mesh - Link
1 x Concrete mixing tub - Link
1 x Melamine panel - Link
1 x 100% Silicone sealant - Link
1 x Small cut section of 1" or similar PVC (for center hole) - Link
1 x 2x4 or similar (screed board)
1 x Sander, Polisher or Grinder
1 x Set of concrete polishing pads - Link
1 x Tarp or plastic sheeting
1 x Concrete sealant - Link

Step 1: The Base

I wont go into to much detail here, you will need a really sturdy base to hold this piece of concrete. I chose to go with this build. It was sturdy enough to withstand the abuse of a 320 lb table top, but still had a nice look and was simple (and cheap) to build.

This choice is entirely up to you, there a plenty of great designs out there that will work perfect for this project. So grab your Kreg jig and some wood glue and make something awesome!

* Don't forget to sand and properly seal your base prior to placing the counter top, especially if this will be exposed to the elements.

Step 2: The Mold

First thing we need to put together is the mold used to form the counter top.

Cut the melamine board to your dimensions, make sure to account for any overlap needed to fasten screws.

I used 4x4 scraps from building the base as stands for the form. This is simply for keeping it off the ground a bit which helps when it's time to get bubbles out of the concrete and eventually removing and flipping the counter top.

Once the mold is cut and screwed together, use silicone to seal all of the seems. This is an important step, ensure you smooth the bead of silicone as nicely as possible. Any imperfections in the surface of the mold will be very noticeable when removed.

If your table design calls for a center hole, this is the time to place the cut piece of pvc directly in the center of the mold securing it with a bead of silicone ensuring to fill in the bottom seem where it meets the form.

* Spray mold with a release or cooking spray

Once the mold is complete and the silicone has dried, cut the rebar mesh to fit inside the mold. Cut the mesh so you have some room between the rebar and the walls of the mold. This will ensure no rebar pokes out of the side of the finished piece. You may also have to cut some of the rebar back to account for the center whole in the counter top.

Step 3: Mixing and Pouring

Get ready to start mixing! Make sure you follow the mixing instructions found on the bag for the given concrete you choose. The concrete I selected was advertised as a "pour-able" mix used explicitly for counter tops. The mixing instructions were way off in terms of the amount of water needed. I found this out the hard way, but after scouring endless online reviews for the product it became clear that the addition of extra water was needed to get the desired consistency.

There are plenty of great tutorials on how to properly mix concrete, a few minutes on youtube and you'll be pretty confident in terms of the amount of water and what the consistency should be for your application.

Start off by filling the bottom 50% of the mold with mixed concrete. Don't be afraid to use your hands (using gloves), make sure you get even coverage of concrete in the mold taking care not to create any air pockets or voids.

Once the mold is filled half way, place the rebar mesh into concrete mix and gently stick it to the concrete. Make sure you keep the rebar at least a half inch away from the edges of the mold. You don't want any rebar sticking out, especially after sanding and polishing.

Continue filling the mold to the top with the rest of the concrete, again make sure to pack in concrete where needed.

With the mold completely filled, grab a 2x4 that is cut long enough to span the two edges of the form. Use the 2x4 to screed the concrete, adding concrete as necessary as you drag the 2x4 across the mold. It helps to use a sawing motion to achieve a nice smooth finish. A second set of hands will go a long way here!

Once the mold is filled, and the surface has been screeded smooth, its time to get any air bubbles or voids taken care of. A good trick here is to use an orbital sander. Vibrate the side of the mold using the orbital sander, repeat this on all sides of the mold. You will begin to see small air bubbles rise to the surface of the mold. You can also use a hammer to strike the edges of the mold to remove any trapped air.

Now, time to dry! This is pretty straight forward, but there are pointers on how to get concrete to dry evenly in your particular climate, I live in a very dry arid climate so I covered my counter with a tarp and allowed it to dry for 4 days. I have read any where from 2 days to 2 months, so follow the instructions on the packaging, but most importantly, use your judgement here. Be patient, the longer you wait the drier and better off the counter top will be in the end.

If you prefer, you can use a wet sponge to further smooth the top of the concrete while its drying in the mold.

Step 4: The Flip: De-molding and Grouting

Now that your concrete is completely dry, its time to remove the mold. Start by removing the screws along the edges of the mold. Once all screws are removed start by gently prying away the melamine sides. This can take some patience, use a chisel or similar inserted into the seems and gently pry away the board, repeat on all sides.

Once all the side are removed, its time to flip the table and remove the base of the mold. Make sure you have some one around that can help you, this is a very heavy piece of concrete!

Now that the table has been flipped, remove the bottom of the mold to reveal the "top" of the counter. Hopefully, if you got most of the air bubbles, you will be left with a nice smooth finish.

Now its time time cover up any mistakes in the finish. unfortunately for me, I didn't smooth the silicone properly and there were several air pockets that I wasn't able to get out with the orbital sander, this is where grout comes in! Use a porter or grout mix of your preference and apply to the counter top using a trowel. Repeat this process on all sides if needed being sure to fill any small imperfections. Finally, once the grout has started to dry, use a wet sponge to further smooth the grout. Allow grout to fully cure before continuing.

Step 5: Polishing and Finishing

Now for the fun part! This is probably the most rewarding step in the process, turning a hunk of concrete in a beautiful shiny counter top.

To get the finish I wanted, i used a set of diamond concrete polishing pads I bought on amazon. There are many sets of these types of pads, just do your research and make sure you buy a set that fits on the tool you will be using. I happened to have a polisher from harbor freight that worked like a charm. I read articles where some people had used grinders with mixed results due to the high speed and aggressiveness. Use what works best for you and your comfort level, but again, be patient and follow the recommendations on the package.

I started off polishing with the 50 grit disc, this was great for getting some of the major imperfections out. I used my garden hose to flow water across the surface while polishing. Continue polishing with the 150, 500, 1500 and finally the 3000. This will leave you with an almost mirror like finish on your counter top.

Once the counter has been polished to your liking, its time to seal the concrete. I used a product I found on amazon to seal the concrete. Simply wiping it on with a rag and allowing it to dry per the specification on the bottle. Once the concrete was sealed, I applied a coat of wax, this is not needed, but it did add a bit of shine and little extra moisture barrier.