Part 2: Pouring and finishing DIY concrete countertops
When you’ve completed all of the prep, you’re ready to mix your concrete and pour!
We used an integral pigment (bright white) with our already white concrete mix supplied by Z-counterform. This makes the resulting product brighter than it otherwise would be. We mixed that in a 5 gallon bucket before adding the concrete per the products instructions.
We found that using ~1 cup of water more than recommended made our concrete the right consistency for us (3 quarts + 1 cup + integral color + 50lb mix of white concrete), we had one section that was poured with the recommended amount of water, and it was slightly stiff. we used a spray bottle of water to help out on that section, and the results look the same on both sections. Concrete is sensitive to how it has been stored (humidity), so the amount of water will vary per lot.
We mixed one 50lb bag of concrete and integral color in a 5 gallon bucket with a joint compound mixer (our drill wasn’t up to the task of using a 4” egg-beater style mixer attachment) until it was a uniform consistency and no dry spots were detectable (you’ll find them when your drill slows down from the bulk mixture).
When the mixture was smooth, we poured the 5 gallon bucket out on to the counter.
We worked the concrete into the corners with the lexan float and leveled it out with a straight board we used as a screed moving it side to side and resting it on the edges of the forms in the front and back.
We added more concrete mixture to any spots that looked low and pushed the concrete away from any high spots to make the surface as level as it could be. At the same time, we tapped the sides of our forms with a rubber mallet. This will help vibrate the concrete and minimize air bubbles. Another method for working out air bubbles is to use a power sander without any sandpaper on it directly on the sides of your form. We found that the rubber mallet was effective for us.
After about an hour, we started using the steel trowel
Keep an eye on your concrete to see how quickly it is setting up. This can take anywhere between one and four hours depending on the humidity in your space. You’ll want to start using your steel trowel to smooth out the top as soon as the concrete is hard enough to no longer jiggle, but soft enough that you can leave an impression if you push your finger into it with force.
Move your steel trowel in a rainbow motion, never pushing too hard around the edges of the form. At this point the concrete is still workable to cover any larger dents and divots, but it gets challenging quickly.
We found the trowel slick to be especially helpful for any problem areas. It’s worth it to take your time with this step and do the best you can, but knowing that the next finishing steps are very forgiving helped reduce the amount of stress I felt about this step.
24-48 hours after the initial pour, it is safe to take the forms off
The drying time depends on a whole bunch of factors, but in our heavily air conditioned house, it was safe for us to remove them in 24 hours. If you’re nervous, just wait another day! 48 hours should be more than enough time. To snap your form off, you just have to use some man power to pry it off. If you’re having a hard time with it, you can carefully slide something skinny down the side to help pry it loosen it.
After about 48 hours you can start the finishing steps.
We used 220 grit sand paper and lightly sanded by hand. We ended up doing about 3 passes for a very smooth finish. The concrete is very easy to sand and really doesn’t require a lot of force. Concrete dust is a known carcinogen and is harmful to breathe in. Wear a mask during this step to minimize your exposure to it. To keep dust to a minimum, I scraped all of the dust off with a credit card every couple of minutes directly into a trash bin. I also used a damp sponge to collect and extra dust at the end to pick up every last bit of dust. Staying on top of dust collection here is going to save a bit of time later.
Next, you can mix a small amount of the counter patch to fill holes.
The counter patch was by far my favorite part of this entire process. Any holes or cracks and every single tiny pin hole will get filled in and will set you up for a very smooth finish. Per package instructions, mix up a small amount (it dries very quickly!) and apply it to any holes with a putty knife. Sand it smooth after it dries.
You can seal your countertop 5 to 10 days after pouring.
The drying times vary a lot depending on your environment. Our countertops were ready to be sealed after 6 days in our heavily air conditioned home. To determine if you can seal your countertops, tape a 12×12 piece of plastic wrap directly on the surface. If it doesn’t “sweat”, you’re ready to seal!
To choose a sealer, I read the FAQs on concretecountertopsolutions.com.
Z SiAcryl 14: Easy to apply penetrating sealer. Satin finish. Will not alter color of concrete or leave thick coating on concrete surface. Best used over highly polished concrete (over 800 grit) or tightly finished/ burnished surfaces. Z Countershine Polish can be added to increase gloss. Can be used outdoors.
Z Aqua-Poxy: 2 part, easy to apply epoxy sealer. Semi gloss finish. Will slightly enhance coloring of countertop without darkening. Put on mulptiple coats to build up thick epoxy look. Not safe for outdoor use.
Ultra ZPoxy: 2 part traditional epoxy sealer. High gloss finish, will significantly darken countertop. Will give you thick wet epoxy look. Can add epoxy pigments or metallic powders to create colors and effects. Not for outdoor use.
Aqua-Thane M35: A water-based polyurethane that forms an impermeable topical shell to offer some of the best stain protection and scratch resistance. Is applied in thin coats with a roller and WILL NOT darken or “wet out” the concrete. Has a low luster matte to satin finsih. Can be used outdoors.
Aqua-Thane G40: A water-based polyurethane that forms an impermeable topical shell to offer some of the best stain protection and scratch resistance. Is applied in thin coats with a roller and WILL darken the concrete. Has a gloss finish. Can be used outdoors.
Each process will be different depending on which sealer you choose. We used Z-Aqua-Poxy and followed the instructions on the back of the bottle. It’s a two part system that is mixed together and applied with a high density foam paint roller.
Overall, we are very pleased with how this turned out! I was intimidated by this project, but the ZCounterform system really does make the project approachable and I really do think anyone can do it! It takes some patience and a thorough read through of the instructions (you’re halfway there if you made it this far!) but really is a great project.
The one thing I would do differently if we ever do this project again is think a little bit harder about the thickness of the cement board. I mentioned in Part 1 that we made a little mistake here and a sliver of our cement board ended up being visible.
To fix this, we cut a thin piece of red oak to tie into the other wood elements in our kitchen and fastened it with silicone caulk. It covers up the cement board and looks intentional. I actually really love the detail and the little moment of warmth it adds, but it definitely wasn’t part of our plan.
This post was written for the Collected Eclectic blog.
Collected Eclectic was a passion project focused on recording the process as Grace and Michael van Meurer transformed their builder grade home in to something special.
124 blog posts were published between 2018 and 2021. Explore the complete Collected Eclectic archive here.
Learn more about the project here.