A beautiful, glossy concrete floor takes time, equipment, and a heavy dose of patience
A glossy, polished concrete floor gives professional and private spaces a sleek, modern look that will last for decades. But if you’re wondering how to polish concrete floors yourself, you’ll need to take a deep look at your skills and the access you have to the specialized equipment needed for the size of your project. Achieving the perfect sheen is a complex process, but it might be doable for the (very) experienced DIYer.
A lot of work goes into preparing concrete floors before you touch a machine to the concrete. You’ll have to grind the concrete, gradually using finer and finer grit until you’ve reached the level of gloss and shine you want. You’ll need diamond grinding pads (or discs) in several grits.
Some of the prep work will depend on the type of machine you’re borrowing or renting. For example, if you rent a concrete grinder with a skirt and vacuum (dust collection system), you don’t need to rent a dust collection system or use your own vacuum to collect dust.
Using a concrete grinder takes some know-how and technique. If you’ve never used one before, practice in an inconspicuous area. You can cut too deeply into the floor if you go too slow but not deep enough if you go too fast.
Check the rotation on the head(s) of the grinder. Pads that rotate in the same direction cut more aggressively, so you may need to increase or decrease the rotation speed depending on the direction of the rotation.
You’ll also need to adjust the speed of the grinder according to the pad’s grit. Coarser grits require lower speeds to prevent the teeth from skipping over the concrete’s surface, whereas finer grits can run at higher speeds.
When using the concrete grinder or edge grinder, wear appropriate protective gear, including safety goggles, dust masks, ear protection, and gloves.
Lastly, consider that your final polished concrete floor cost will depend on several factors, such as the size and shape of the concrete, the concrete’s thickness, and the final look you’re trying to achieve.
Use a Mohs pick and scratch test kit, and following the manufacturer's directions, test the concrete to see where the concrete falls on the Mohs hardness scale. The concrete’s hardness determines the grit you need.
You’ll have the best success by buying all the grinding pads from the same manufacturer. Each manufacturer has its own system for rating the pads and the corresponding concrete hardness they work best on.
Cleaning concrete is easier than polishing but no less crucial to the final result. Sweep or vacuum any dust, debris, or dirt from the concrete’s surface. Apply a concrete cleaner to remove adhesives or other chemical substances that could interfere with polishing. If the concrete has an existing coating, you’ll need to grind it off using the concrete grinder.
Using a trowel, sponges, float paddles, and epoxy, grout, or another semi-rigid filler, seal any cracks or holes. If left untreated, they can change the consistency of the final finish.
Using the concrete grinder, attach the coarsest grit (lowest number) diamond grinding pad, and methodically grind the entire floor. You may need an edging grinder for square edges to complete the floor. If it's a smaller project, use a hand grinder instead of a walk-behind concrete grinder.
Change the grinding pads to those with a finer grit. For example, if you started with a 30- to 40-grit pad, go to an 80-grit on this pass. Do another pass over the entire floor with the finer grit pads. After your second pass, get ready for a third. This time, use a finer grit yet again. For example, if you used a 40- and then an 80-grit pad (as described above), you can move on to a 150- to 200-grit grinding pad.
A densifier is a chemical hardener that contains silicate materials that react with the concrete to harden the floor, creating a protective top layer. It also reduces dust and improves the concrete’s strength. The product may be called a “densifer and hardener” or simply a densifier or hardener, but they all do the same thing.
Spray on the densifier while another person uses a microfiber mop to evenly spread it. The densifier may reach a point where it gels or pools, at which point, you can either spread it with the mop again to break the surface tension or add a small amount of water to that area to help the densifier penetrate the concrete.
Allow the densifier to dry according to the manufacturer’s instructions. Densifiers generally take about 24 hours to dry, but environmental conditions may shorten or lengthen drying time.
By now, you know the drill. Using the concrete grinder, polish the floor with a 400-grit diamond grinding pad.
This step will depend on the final look you want, and some people may choose to skip applying another layer of densifier altogether. You can:
Apply a final light densifier layer.
Apply a coloring agent, stain, or dye before applying a light densifier layer.
Some pros apply a light densifier layer to help lock in the color, while others don’t.
Change the pads to an 800-grit, with the option of gradually using pads up to around 3,000-grit until you’ve reached the desired level of polish. You may not need to use the finer grinding pads, depending on the desired look and hardness of the concrete.
Do another pass over the entire floor with the concrete grinder with the finest grit pads you’re going to use. This step is where you’ll create the glossy finish. You may need to repeat steps 10 and 11, using increasingly finer grit grinding pads.
There are many options when looking at how to seal concrete, from polyurethane to acrylic and epoxy sealers. Choose a sealer or stain guard based on where and how the floor will function. Use a sprayer and microfiber mop or roller to apply the sealer.
Polishing concrete floors is a long and complicated process that requires costly equipment. Everything about concrete, from its hardness to the climate and whether it’s a new or old floor, affects the polishing process. (You’ll need to factor in concrete slab costs if you’re dealing with a new pour, too.) Unless you have experience polishing concrete floors, you’ll get the best results by contacting a local concrete pro. They can determine the right pad grits, densifier, and sealer to achieve your desired look.
Yes, you can polish an old cement floor. However, be aware that the first pass with the concrete grinder may reveal a few surprises and imperfections. You may also have to contend with the consequences of previous floor coverings, such as tile or carpet, which can leave a pattern in the concrete. Old concrete is more likely to produce uneven results if you want to use a dye or other coloring.
Polished concrete gets its glass-like finish from several rounds of polishing, using increasingly finer grit diamond grinding pads. The concrete’s hardness will determine which grits you need to get your desired finish. The densifier and sealer also contribute to the look of the final floor, so either talk to a concrete pro (or hire one) to achieve the right concrete floor finish.
