How To Sand Concrete: Complete Guide

Given its hardness and tremendous durability, it doesn’t seem like it would be possible to sand concrete. But despite these characteristics, concrete isn’t as hard to sand as you might think. You can use a disc or belt sander or concrete grinder combined with standard sandpaper discs or diamond encrusted pads to sand concrete to a shiny finish.

There are plenty of good reasons to undertake such an arduous project. Sanding concrete is a good way to improve the look of concrete or remove sharp inconsistencies that can make a patio, countertop, or driveway unsafe.

In this article we’ll discuss how to sand concrete and provide step-by-step directions for completing a concrete sanding job.

Why Should You Sand Concrete?

While sanding concrete may sound like an arduous process, there are several good reasons to undertake this project. Sanding concrete can improve its overall appearance, make the surface safer, and ensure smooth following repairs.

Benefits of sanding concrete:

Improve Appearance

We use concrete to create patios and countertops and driveways, all of which are areas in which aesthetics are very important.

Whether it’s floors, walls, or a kitchen countertop, sanding concrete can dramatically improve the appearance of a concrete surface by removing inconsistencies, eliminating stains, or even changing the texture of the concrete by giving it a different finish.

Remove Dangerous Edges

After pouring concrete, corners can create edges or uneven parts that jut out dangerously from the surface. All of these create potential hazards that can injure someone walking on the concrete or, as in the case of a driveway, even damage tires. Sanding these spots smooth can make a driveway, patio, walkway, or even countertop safer, not to mention more visually attractive.

Remove Paint

While there are chemical methods such as paint strippers and cleaners to remove paint, sometimes they aren’t enough to do the job. Sometimes you need to remove an entire layer or two of concrete to get the job done, where sanding comes into play. Sanding is an effective way to eliminate paint, although it should be noted that it can change the texture of the concrete depending on how much material is removed during the sanding process.

Make Repairs

Cracked, pocked or chipped concrete that needs repairs typically needs to be sanded after those repairs are made to achieve a smooth and uniform look. Remember that it’s very difficult to match the filler with the existing concrete, so you may need to apply paint or stain after sanding.

Can You Sand Concrete?

Given that concrete is a hard and durable surface capable of enduring tremendous abuse, it may be hard to believe that one can sand it. With the right tools and supplies, concrete is sandable. And while it may not be a surface you want to attempt to manually sand, unless it’s a small area, power sanders and grinders are very effective at smoothing out the surface of the concrete.

You can sand any concrete surface, whether it’s a wall, countertop, driveway, patio, or basement floor.

Can You Sand Concrete With Regular Sandpaper?

It is possible to sand concrete with regular sandpaper. As with wood, discs designed to fit concrete sanders come in varying grits to remove larger amounts of material or polish concrete to a smooth surface. The key is to use sandpaper with the right grit.

Best Way to Sand Concrete

You can use several tools to sand concrete, ranging from manual sanding blocks to large floor polishers. Below, we’ll describe each tool so you can make the best choice for your project.

Hand Sanding Concrete

Hand sanding concrete is a great option for smaller irregularly shaped objects. It allows you to get into nooks and crannies and around curved surfaces that mechanical sanders would not be able to get into. Hand sanding is also suitable for decorative objects that cannot be safely sanded with a large angle grinder or belt sander.

Of course, hand sanding is much more laborious as it requires your arm to do all the work. For this reason, it’s not feasible to sand large surfaces such as a driveway or patio. Even sanding a concrete countertop by hand can be quite laborious and time-consuming. It can also be difficult to sand large surfaces easily when done by hand.

Belt Sander

A belt sander consists of a motor with two drums that spin a loop of sandpaper around at high speeds. There are stationary belt sanders, in which material is held against them, and handheld belt sanders, which the user applies to the material. The latter is suitable for sanding concrete.

A handheld belt sander is a great option for flat surfaces, making it ideal for sanding down countertops. It’s powerful enough to remove large amounts of material to remove inconsistencies and, when used with fine-grit sandpaper, can polish a countertop to a shiny, smooth finish. It’s also relatively easy to get a consistent finish with a belt sander.

Since handheld sanders are still relatively small, they’re not suited for larger surfaces, such as a patio or garage floor.

Angle Grinder

An angle grinder consists of a motor with a grip on the body, a handle on the side, and a circular grinding blade. Angle grinders were originally designed for grinding down metal, but they also work well well with cement. They range from 4-1/2 inch blades to 9-inch blades.

Since grinders use hard discs versus softer sandpaper, they’re capable of removing more material at a time than traditional sanders. This makes them ideal for surfaces with significant inconsistencies. They also produce a significant amount of power, making them capable of polishing concrete to a smooth finish when equipped with fine-grit discs. And, since they can cover more ground more quickly, they’re suitable for larger projects.

With great power comes great responsibility. In this case, because an angle grinder can remove more material more quickly, it’s easier to create gouges or inconsistent areas in the concrete than it is with sandpaper if one isn’t careful in how they use it.

Orbital Sander

This type of handheld sander operates in a random circular pattern, making it easier to move in all directions, unlike a belt sander that can only be moved forward and backward. This makes the orbital sander ideal for sanding certain surfaces, such as a countertop or even concrete bathroom floor. Since the orbital sander gives the user a freer range of motion, it’s easier to use than other sanders.

Just keep in mind that not all orbital sanders are created alike. Weaker orbital sanders may not produce enough power to put much of a dent in concrete. Choose a higher power orbital sander that has enough amps to chew through concrete.

Floor Concrete Grinder

Floor concrete grinders are large machines on wheels with a large grinding wheel that measures about 10 inches in diameter. You operate a floor grinder by pushing it from standing when the motor spins the grinding or polishing pad. Due to their size, floor grinders are ideal for sanding large surfaces, such as an entire driveway or a large patio. These machines are expensive to purchase but can be rented for a reasonable price.

Best Sandpaper for Concrete

Whatever tool you plan to use to sand concrete, it’s crucial to select the right grinding pad, disc, or sandpaper.

To remove a large amount of material to level inconsistencies or alter the look of the concrete, start with a courser 40-60 grit sandpaper. To smooth concrete that has few irregularities in it, start with 80 to 120 grit sandpaper. If you’re simply trying to achieve a smooth finish, use sandpaper with a grit ranging between 200 and 400. If you want the concrete to have a shiny finish, you’ll need to gradually increase the grits up to 800 or more.

How to Sand Concrete Floors or Countertops

Once you’ve decided what tool you plan to use for sanding the concrete, it’s time to begin the process. Below, we’ll detail each step you should take to complete a concrete ending project.

Step 1. Prep the Room and Yourself

Begin the process by protecting any furnishings that can’t be moved out of the area with plastic sheeting. Since sanding concrete will fill the air with harmful dust, it’s essential that you wear a respirator and use goggles or safety glasses that completely enclose the eyes. Since concrete has silica that can irritate the skin when pulverized into small particles that can fill the air, wear clothing covering all exposed skin.

Step 2: Inspect and Repair

Inspect the concrete surface for any cracks or chips and repair those areas using a concrete filler. Allow the filler to dry completely before proceeding with sanding.

Once dry, clean the area with a mix of water and a household detergent. Use an industrial strength cleaner, such as hydrogen peroxide, TSP, or ammonia to clean any stains on the concrete. Wear gloves and eye protection when handling these chemicals and make sure the area is well ventilated.

Step 3. Choose Your Sandpaper

Choose either sandpaper or turbo cups to begin the sanding process. Both come in a broad range of grits ranging from coarse to medium to fine.

If you’re using a handheld grinder, you can use turbo cups, consisting of a metal disk and an edge encrusted with diamonds. Turbo cups, which are between 5 and 6 inches in diameter, can cut through concrete more quickly than sandpaper, allowing the grinder to remove more material with each pass.

Like sandpaper, turbo cups come in different grit levels. The lower the number, the more coarse the disc is.

If you need to remove a thicker layer of material to achieve the desired finish, consider a handheld grinder and turbo cup. If you plan to do minimal sanding and polishing, then go with an orbital sander and sandpaper.

Another option is diamond pads. Diamond pads consist of thin plastic encrusted with diamonds. They are less aggressive than cups and therefore less productive. They come in grits ranging from 50, which is coarse, up to fine 3,000 grit, ideal for polishing surfaces.

Whether using sandpaper, diamond pads, or cups, it’s important to follow a certain progression when sanding. Begin with coarse-grit of around 50 and continue gradually to finer grit levels by moving to 200 then 500 up to 3,000 for polishing. Don’t attempt to skip ahead, as very fine sandpaper will not be coarse enough to remove the scratches created by 50-grit sandpaper.

When choosing your sandpaper, consider what kind of finish you’re after. Smoothing the concrete involves polishing the surface’s top layer to a smooth finish. The finer the grit you use to smooth the surface, the shinier it will become.

A more aggressive sanding job involves removing a small part of the surface’s top layer, exposing the sand below. This gives the concrete a salt and pepper finish.

A more thorough sanding that involves removing a significant amount of material will create an exposed aggregate finish, making the aggregate that comprises the concrete visible. To get this type of finish, you’ll need to use either an angle grinder or floor grinder, depending on the size of the job.

Step 4. Start Sanding

Before you begin, decide whether you’ll use a wet or dry method. Wet sanding uses water as a lubricant during the sanding process. This helps reduce friction, keeping the pads cool so they last longer. It also helps to minimize dust by wetting it down, minimizing the amount of dust that ends up airborne.

Wet sanding is also messy as it creates a slurry that you must clean up and dispose of periodically as you sand and uses quite a bit of water, which is wasteful. It’s also difficult to achieve a glossy shine when using this method.

Dry sanding allows you to achieve better results, especially if your concrete surface has a glossy finish. It wastes no water and creates no pasty substance that you have to clean up afterward. And while dust is certainly an issue, these days, many concrete grinders and polishers have dust extraction systems that help collect dust as they sand, minimizing the amount that ends up in the air.

Begin sanding using coarse grit to remove any inconsistencies or stains. Once the concrete is stained-free, move on to a finer 80 grit sandpaper or grinding disc. Make sure to cover the entire area, moving from one corner to the next corner.

Once you’ve finished sanding the concrete with the 80 grit disk or sandpaper, move onto a finer 150 grit, followed by 200 then 400 grit levels. While 400 is often enough to smooth concrete to a shiny finish, you may wish to go to an even higher grit level if you aren’t satisfied with the finish. Before moving onto a finer grit, make sure you’ve removed all the scratches created by the previous pad.

Step 5. Apply a Hardener

Once you’ve completed the sanding, apply a chemical hardener. A hardener will solidify the concrete to create a durable finish that will better hold up to wear and tear. If you have medium hardness concrete, apply it after using an 80 grit disk. For harder concrete, don’t apply the hardener until after using a 200-grit disk.

You’ll need a sprayer to apply the hardener evenly over the surface.

Step 6: Polish

Wait for the hardener to dry, then polish the concrete surface using a 3,000 grit disk or sandpaper, making sure to cover the entire areal. This high grit sandpaper or grinding disk will polish the concrete to a high gloss surface.

Remove any dust from the surface and use a buffer to complete the polishing.

Step 7. Apply a Sealant

Give the countertop plenty of time to dry, especially if you used the wet method to sand or grind it, then apply a concrete sealant. This sealant will protect the surface you’ve worked so hard to restore from oil, grease, water, and other fluids that can stain it.

How to Sand Concrete Walls

As with the above method, begin by cleaning the walls with dish detergent and water. To remove stubborn stains, use an industrial-strength cleaner. Allow the wall to dry, then use a handheld grinder with a diamond sanding pad to sand the wall.

Apply even pressure to the wall moving back and forth and up and down from one end of the wall to the other, making sure not to miss a spot. As above, begin by using coarse grits before moving to finer grits to polish the wall to a smooth finish. When complete, make sure to add a hardener and a sealant to protect the wall from future stains.

How to Sand Concrete Patio

Begin by removing all furniture and grills from the patio, then cover any nearby landscaping with drop cloths to protect it from the concrete dust. Use a broom to remove any debris from the patio floor. If needed, remove any stains using a solution of dish detergent or chemical cleaner.

Load the sanding disks onto an orbital floor grinder. Pass the grinder over the floor, moving from side to side to remove inconsistencies, cracks, and other imperfections while smoothing the surface.

Add finer grit disks moving from 300 to 800 until you achieve the desired finish. For a glossy sheen, use a 1,500-grit disk. Clean up by using a shop vacuum to remove any concrete dust.

Use a power washer to thoroughly clean the patio, then allow it to dry for about two days. Apply two coats of penetrating sealer to the patio using a long-handled roller brush.

How to Polish Concrete by Hand

Although polishing concrete using a machine is perhaps the preferred method for sanding concrete, it is possible to do so by hand. In some cases, polishing concrete by hand is the best way to go.

To do so, you’ll need the right tools. Conventional sandpaper isn’t hard enough to make much of a dent in concrete when polishing by hand. Diamond polishing pads, such as these from Toolocity, are the best option.

These diamond-encrusted pads are hard enough to cut into the concrete surface. As with power methods, when sanding by hand, you’ll want to start with coarse grit and gradually move to finer grits. Make sure not to jump too far ahead, as finer grit sanding blocks will not be able to remove the scratches created by course blocks.

Do You Have to Seal Concrete After Sanding?

While you don’t have to seal the concrete after sanding, if you’re going to spend all that effort to sand and polish concrete, it only makes sense to do so. Concrete is porous, which means it easily soaks up fluids. This means oils and chemicals can easily stain concrete. It also makes it more susceptible to cracking and chipping.

Sealing concrete makes the surface resistant to fluids, hence protecting it. Not only does sealing protect the concrete’s surface, but it gives it a finished look by adding a glossy finish and deepening its color.

Conclusion

There are plenty of good reasons for sanding concrete. Sanding concrete improves its appearance and makes it safer by removing sharp edges. It’s a good way to remove paint and stains from the concrete. And, it’s also a necessary step to smooth the surface after filling cracks or chips.

Although concrete is very hard, fortunately, there are several ways to sand it, ranging from orbital sanders to concrete grinders to even handheld sanding pads. Whatever method you choose, make sure to take the proper safety precautions by using a respirator and goggles and keeping exposed skin covered.