First time concrete countertop project? We've been there for thousands of customers as they begin this step. Whether you are a homeowner doing a DIY concrete countertop, or beginning the process of starting a business, the steps begin the same:
First thing is decide how you want to make your concrete countertop. You can make it right in place, on the cabinets. Or you can make it precast, in forms, and install it when done.
Cast In Place Concrete Countertops: Pros: No heavy pieces to move/install. No seams. Ideal for large projects, kitchens, island bars. Cons: Requires more work setting up forms. Requires more time waiting on-site to finish the concrete (trowel it smooth), and can take some skill with a trowel for a really good finish.
Precast Concrete Countertops: Pros: Easy to set up forms. Finished pieces will be perfectly flat and smooth. No troweling or babysitting the concrete once the form is filled. Cons: Can be heavy and hard to move/install. Multiple slabs will have seams.
Got a plan now? Good. Now to implement it. Cast In Place Countertops should start by looking at the forms we carry that you screw onto your cabinets (screw down 1/2" concrete board to the top of the cabinet bases first): Cast In Place Concrete Forms sold here. If doing Precast Countertops, the basic process is outlined on another page on our site, seen here.
We've compiled a really basic catergory of products that are more or less the 'essentials' to get a concrete countertop made. By no means is this a perfect list, and there are plenty more products on our site to look into as well... but maybe do that on Round 2. Click here for the Concrete Countertop DIY Products.
Once your forms are set up, use a high strength concrete mix, using pre-made concrete mixes or admix that you add to locally purchased bags. We sell Concrete Countertop Mixes/Admixes here. We also have a Concrete Countertop Recipe Page here, to help guide you how to make your own high-strength concrete mix.
Most of the products on our site here will help you use them, if you read the product description, and many of the products also have videos to help understand the use for that product. If a product has a TDS download, make sure to download/print it. This is the Technical Data Sheet, aka the INSTRUCTIONS. Yes, we know, reading hurts, but so does using a product incorrectly.
Reinforcement? This is a very common question we get asked. Simply put, just do it. If you are wondering if you need to, or can get by without... just do it. Once you are a pro, you'll know when and what you can get away with. For now, add the rebar to your form. Use the fiberglass scrim fabric. Use the chopped AR Glass Fiber in the concrete mix. The guy who said afterwards that they regretted adding extra reinforcement... never happened. The guy who said they regretted not adding extra reinforcement once a piece cracked, or broke, happens quite often.
One side tip here on reinforcing concrete with Chopped AR Glass Fiber. The fiber is big, and you don't want to see it. In Pre-Cast, you wont see it so no worries, unless you polish the concrete down into the sand- then you can start to hit some fibers. If this is your plan, consider coating the bottom 1/4" of the Precast Form with concrete that has no fiber, or even a sand/cement mix (no gravel), and then use the fiber in the rest of the concrete. For Cast-In-Place concrete, you can fill the forms up most the way with fiber-concrete, but leave the top 1/2" unfilled, wash out your mixer, buckets, and trowels, and then mix concrete with no fiber (or again a sand/cement mix), as a fairly dry mix (about like thick oatmeal) and finish filling the form by hand dropping the mix all over the form, trying to avoid pushing the top layer sideways- just push it straight down with a magnesium trowel. If you still get fiber when troweling, then your mix is too wet and you'll just have to pick out the fibers as you see them while troweling.
Now we'll assume you have created your concrete mix, and filled your forms. To help the concrete gain strength, while reducing shrinkage (cracks), wet-cure the concrete for the first 2 days. Cover the concrete with plastic, and keep it wet by spraying water on the concrete a few times a day
(Covering the surface of Cast In Place concrete with plastic can cause uneven coloration, which is usually fine and a cool part of concrete, but if you want to minimize this just cover the concrete with thin plastic, and make the plastic lay perfectly flat on the concrete with no air trapped areas, or wrinkles in the plastic)
Waiting to demold the concrete piece is sometimes like waiting for Christmas morning as a kid! If you get this feeling, then you are on the right track and should consider a profession in Concrete Countertop fabrication. Some mixes can be demolded in hours. Most should wait 48 hours though. If you demold too soon, the concrete can be more fragile and crack or parts peel off with your forms. If you wait too long (mostly just with Precast) the concrete can begin to curl, which happens when one side of a slab is drying faster than the other- the part still in the form- and the concrete will curl, or curve, towards the drying side. A bowed countertop is not a good thing, so wet-cure to slow the curing down for 48 hours about, and then demold. Cast In Place- simply remove the edge forms and no longer cover in plastic. Precast- remove side forms and flip over, resting the slab on some risers so air can move under the slab as well.
Once the concrete looks dry (usually day 3) you can sand the concrete. This should be done to all concrete countertops. 200 grit sandpaper on a regular palm/orbital sander is good. Change the sandpaper every 10 square feet about, even if it still seems good. You want a 200/220 grit finish on the concrete so your sealer bonds good. Running sandpaper too long will lessen the grit. This sanding step is important to open any small holes hiding just under the surface. You don't want to have these holes open up later, so find and fill them now with Slurry. After filling with slurry, you can sand again a few hours later, and assess if you need to slurry another coat. Mist the slurried surface with a spray bottle of water every 15 minutes if you want- it helps it dry a little stronger. Back to sanding- For Cast-In-Place countertops, this sanding step is vital because a steel trowel can make the concrete surface VERY smooth if done long enough, and correctly. So sanding is required so the sealer works right. Sanding will also help remove any minor imperfections in the concrete surface from your steel trowel finishing. Alternatively, you can polish with diamond pads to expose sand, aggregate, glow in the dark glass, etc. Dry Polishing pads work fair, but wet polishing is always more efficient, and often worth the work of the mess and clean up. Again, polish just to 200 grit. Higher grits, which we do sell, are for natural stone like marble and granite, and use a different sealer (penetrating only sealers).
Now you can stain, if desired. Usually this is by day 5. (You can also mix in colorant with the concrete when you fill the forms). Water Based stains are great, and can be brushed, rolled, sponged, or sprayed from an HVLP sprayer (best way). Some people have had problems with water based stains not staying on the concrete, which is caused by the concrete not being 'open' to take the stain. Open the concrete by sanding with 200 grit sandpaper...! Or, use an Etch-Prep product. Acid stains are well suited for mottled looking patterns, and multiple colors can be used for more color variety. To use multiple stain colors, apply them to the concrete side-by-side, and if you puddle the acid stain, the puddles will bleed into each other for a cool look. Acid stains etch the concrete as they stain, so sanding first is not required (but you still should sand to open and fill the holes with slurry!). Acid stains have to be cleaned well, and neutralized to remove the acidic PH level, and cleaned again. Water based stains can just be applied, and when dry you can seal the concrete- so another cool advantage! One side note- staining concrete that isn't fully cured (28 days usually) can color slightly different. If doing multiple slabs, you want to stain them the same amount of time since they were made. So if you stain on day 5, make sure any other slabs, even if made later, are stained on day 5- assuming all other conditions (temperature, concrete mix, curing process, etc.) are the same.
Give the concrete a few extra days to keep curing. If possible, give it a week! Most don't want to wait that long, and apply a sealer around day 7. Most sealer problems come from moisture in the concrete though, so if you have the time... give that time to the concrete allowing it to cure out the moisture. The sealer XS-327 is perfect for any concrete countertop- indoor or outdoor, kitchen or bath, fireplace or furniture. It's water-based, so you add water to mixed sealer and that makes it cover a lot of footage. You can easily seal 100 sq. ft. of concrete from one 40oz. kit of the XS-327 sealer, and that's counting on you doing all 3 coats as specified in the sealer instructions! The sealer is dry to the touch usually the next day, and can carefully be used. It will get harder each day for a week. Pre-cast can usually be moved and installed the next day, but may require an extra day or two before you can move it- depends on your temperature and humidity. The sealer cures faster with humidity, so feel free to add a humidifier to the room while it cures.
When all done, you probably have a few things you don't like. This is good! It means you learned a few things, and didn't even have to pay someone a few thousand dollars to take their 'training class' for how to make a concrete countertop!
Still anxious? Start small. Make a coffee table. Make a bench. If you hate it, you're out $20 in material and a few hours of your time, but that is time well spent as this is one thing that you can say practice does make perfect.