The particleboard is what you use to create a non-stick container called a form. It’s an important part of shaping and fitting the countertop. Make sure it has a melamine coating so the concrete doesn’t stick to it! Melamine-coated particleboard, along with everything else you might need for the installation, can be found online. It’s also available at most hardware stores.
If you’re not installing over cabinets, then find an alternative way to estimate the countertop size. For example, standalone and outdoor countertops sit on some sort of base. Measure the base to figure out the perfect countertop size for your home. Take separate measurements for each countertop you’re installing. For example, if you’re installing countertops in a corner, you will usually install 2 separate countertops instead of a single, big one.
To limit the amount of cutting you have to do, work along one edge of the board. You can repurpose it for one edge of the form. Take advantage of one of the longer edges! If you’re planning on scoring the melamine, trace the outline on both sides. Scoring the board first will ensure you can cut through it more cleanly than usual.
If you’re able to, work outdoors in order to limit the amount of sawdust that gets into your home. You can vacuum afterward to remove the leftovers. Remember to keep other people and pets out until you’re done working and have had a chance to clean up.
Always score both sides. If you only score one side, the other side can still chip. It may make the form weaker when you use it to create the countertop.
It’s best to leave the particleboard a little longer than you need it. That way, you can easily set the form on top of it to mold the countertop. You could also use a table saw if you have one available. If you’re using a table saw, carefully push the particleboard toward the blade. When you’re done cutting everything, you should have enough boards to build into a frame. When you set them on top of the board you cut for the base, you will have a container to pour the concrete into.
Also, outline any other spots where you will have a hole in the countertop, such as for the faucet. Determine where the sink and other components will be before continuing. Another option is to get high-density foam. Set the sink or sink template on it, then trace around it with pencil. Cut it with a serrated knife, then place it in the cutout spot and pour concrete around it. Cutouts are used to leave holes in the countertop. Frame them with particleboard, then pour concrete around them.
Make sure the strips are as tall as the finished countertop will be. If they are too short, they won’t be able to hold all of the concrete you need for the installation. Test the boards by placing them along the first board. They should fit cleanly together. Make sure they are the perfect size, since you will use them to shape the countertop. If you are going to install a faucet, try cutting a piece of PVC pipe. Make it the same size as the bottom edge of the faucet.
The easiest way to make the frame is by setting the smaller boards on top of the base board. If you don’t have enough room on top of the particleboard, place the strips around its edges in a frame.
Make a separate frame for each cutout you want the countertop to have. If you place them outside the outline, the hole left in the concrete will be too big. Your sink, for example, might fall straight through when you try to install it.
Another option is to make the marks on top of the strips. You can then screw down through them to ensure they are nice and snug against the base board.
The pilot holes are a great way to prevent the boards from cracking when you screw them together. It is possible to screw them in place without pilot holes, but they may crack before you’re done with them. Try measuring about 1 1⁄4 in (3. 2 cm) up from the tip of your drill bit and then wrapping a piece of masking tape over it. You can use the tape to determine when the pilot holes are deep enough. Always use a drill bit that is one size smaller than the screws you plan on using to secure the form boards together.
If you’re having a hard time fitting the strips together, you could spread hot glue underneath them and along their edges. Glue is particularly useful for interior strips, like the ones you might use to outline a sink cutout. To help keep the strips in place, you could also place some scrap blocks of wood next to them. Screw the wood to the side and base boards for additional stability.
Silicone and polyurethane caulk are the best choices. They are waterproof and will stop the concrete from leaking out of the form. Apply the caulk along the inner edges of the form boards or else you won’t successfully seal off the gaps. The caulk helps ensure you end up with a smooth countertop that looks great wherever you place it.
If you use concrete specifically designed for countertops, it will have filler and additives that help it last longer. Make sure it’s a high-strength, pre-mixed concrete so you aren’t stuck waiting forever for it to dry. To determine how much concrete you need, multiply the length, width, and depth measurements of your countertop together. Search for a concrete calculator online to take care of the math for you.
You could also fill the wood form as much as ⅔ of the way full before smoothing out the concrete and laying mesh on top of it. It just needs to be at least halfway full to ensure it’s durable enough. If you’re making multiple countertops, pour them individually. Make sure they are separated by particleboard, or else they could end up fused together.
It’s a good idea to push the concrete down a few times with a hoe. If it isn’t packed in very well, the countertop will have air holes that weaken it.
The mesh is very easy to place. All you have to do is gently set it on top of the fresh concrete. It makes the finished countertop much less likely to crack. Cutting the mesh could leave sharp edges behind, so handle it with caution. Wear cut-proof work gloves for additional protection.
You could also shake or hit the particleboard with a rubber mallet to compact the concrete. Be sure to pour more concrete afterward as needed to fill in any gaps.
Use the edge of the trowel to push concrete into any gaps you notice along the particleboard. Make sure the form is packed as fully as possible so that your countertop is solid and strong.
If you have the time, you can leave the concrete to dry for longer. It gets stronger as it finishes curing. Try leaving it alone for at least a week. Many types of concrete take up to 28 days to fully cure. You can wait that long if you have the time, but it isn’t really necessary. Besides, the particleboard becomes more difficult to remove as the concrete hardens.
If some of the concrete falls off, put it back on with a trowel. Spray it with a little bit of water to make it easier to work with. Then, wait longer for it to dry.
To make this part easier, use an orbital sander. You will be able to smooth out the countertop much quicker and even get a better finish than usual. If you have to sand off any bubbles, you can fill them in with a concrete patching compound. Let it dry for 4 to 6 hours before sanding it flat.
If you have a HEPA vacuum, you can use it to suck up the dust. Regular vacuums likely won’t remove all of it, but a HEPA vacuum is designed to trap small particles like unseen dust. Washing and sealing concrete is a messy process. To keep your home clean, take the countertop outside and lay it on a plastic tarp, if possible.
Another way to apply sealant is by using a sprayer. You could also use a clean cloth to wipe the sealant on.
If you have time, you can apply another layer of sealant to both sides to ensure the countertop is completely protected from stains.
Keep in mind that the concrete may not dry out evenly. If you have it flat on a tarp, the bottom edge could still be damp. Wait a little longer or flip the concrete back over to finish drying it.
If the new finish makes the countertop look a little dull, you could wax it to give it a shine. Wipe the wax onto it with a clean cloth. Some sealants give a high-gloss sheen like wax does, and you don’t have to shine your countertop if you don’t want to.
The countertops don’t actually attach to the cabinets at all. However, they are so heavy that they won’t move. Concrete countertops may need additional support because of their weight. [33] X Expert Source Sarah FogleDIY Specialist Expert Interview. 10 August 2021.
