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Can You Sand Concrete Walls? [And How To]

Most concrete walls have a dull, unfinished look. If you're trying to make a space feel more liveable, concrete walls can be a tough obstacle. But can you sand concrete walls to give them a more polished appearance? We've checked with masonry experts for all the details and have the answer for you.

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You can sand concrete walls, though you'll need to follow the correct process. That said, sanding concrete also requires the right tools. However, you can sand concrete walls to a high shine when done right, so this may be worth trying.

Keep reading, and we'll cover everything you need to know about sanding concrete. First, we'll explain what you need to think about before you begin. Then, we'll go over the right tools for the job. Furthermore, we'll explain all the steps to refinish your concrete wall. Finally, we'll go over some common questions people have regarding concrete.

Sanding the concrete wall with a big sanding paper, Can You Sand Concrete Walls? (And How To)

Can You Sand Concrete Walls?

For a more finished appearance on your walls, you can sand concrete. With the right tools, sanding can be relatively easy.

Just follow the correct process, and you'll have a smooth, flat wall in no time. Sanding concrete can be done either wet or dry. This depends on the tools you are using. You'll also need to consider the desired finish.

Interior of an empty basement with tan walls and recessed lighting

A salt-and-pepper finish creates a speckled look. Taking this speckled appearance a step further is the aggregate finish.

The salt-and-pepper finish removes about 1/16th an inch from the concrete surface. Compared to the aggregate finish, this is the least, which removes as much as 1/4th of an inch.

Finally, there's always a smooth finish. This, of course, is the most labor-intensive method; however, if you want to paint next, this provides the best surface.

How Do You Smooth A Concrete Wall?

There are several tools that you can use to smooth a concrete wall. These include walk-behind sanders and angle grinders.

However, to smooth a concrete wall, use a concrete surface grinder. Compared to a walk-behind sander, you can hold a hand sander vertically to the wall.

Concrete surface grinders cover a large area. If you don't have access to one, you can also rent them.

Angle grinders can be used for smoothing small spots or irregularities. However, they only cover a small surface. For this reason, it's tough to use for an entire wall with consistent results.

Smoothing a concrete wall isn't very complicated. However, it takes a lot of elbow grease. The steps include:

1. Determine Wet Or Dry Sanding

The tool you use may indicate whether you want wet or dry sand. Either one is compatible with concrete. Some devices have special vacuums for collecting dust. This way, you can dry sand without a lot of mess.

Other tools come with an attached hose. This provides a steady flow of water ideal for wet sanding.

If your tool isn't designed for one or the other, you can pick yourself. Wet sanding is great if you're going to be taking off a significant amount of concrete.

Cutting the concrete with a huge grinding machine

The water helps extend the life of the sanding pad. It creates a rather dull finish, but you can always dry-sand the final layer to add some shine.

More modern tools do not necessarily require wet sanding. They're advanced enough to handle a tough concrete surface dry without excessive wear to sanding pads.

Some people prefer wet sanding, as it's how they learned to sand concrete. Others argue that unnecessary waste of water is environmentally unfriendly. In the end, it's up to you. Most experts ultimately agree either process is fine.

2. Preparation

If you're dry sanding, expect a lot of dust. If you're wet sanding, the process creates a liquid slurry from the damp concrete dust. Either one will be messy.

Be sure to cover and protect nearby surfaces. For wet sanding, cover the floor well. If the liquid mixture dries on a surface, it becomes tough to clean or remove.

Wear adequate protection over your clothes, as well. Furthermore, be sure to have goggles to keep dust out of your eyes.

3. Check The Surface, Deal With Big Flaws

Before you begin sanding, you first need to check over the wall. If there are significant problems, then deal with them. For example, patch any cracks if necessary.

If there are any big, uneven flaws, sand those down now. You can do this by hand or with a tool. Generally, the size of the area will indicate which is better.

Just remember, you want a relatively even surface before you sand the entire wall.

4. Start Sanding

You'll start with the lowest disc or attachment for your sander for the first round. The lower numbers correspond to coarser grit sandpaper. Always begin with coarse sanding, moving up toward a finer finish later.

First, use your tool to cover all areas equally. Try to keep the pressure even and consistent.

Worker sanding the concrete wall

4. Do Areas By Hand If Necessary

You may find some areas that you can't reach with your grinder. You can then do these by hand. Just use a sanding pad.

Make sure it is similar in grit to the grinder attachment. You want the finish to match the rest of the surface.

5. Continue Sanding

Increase the sanding power by changing to a higher grit disc or attachment. Cover the wall again, completely covering the surface. The polish over scratches from the previous sanding by going across them perpendicularly.

The desired finish will determine how many rounds you must do in all. Continue to increase your sanding grit, getting a finer finish each time. Always cover the wall entirely before changing attachments.

6. Use Liquid Chemical Harder

To keep your surface strong, you'll want a liquid chemical hardener. This is especially important if your wall is older. You don't want to lose any integrity or durability of your concrete.

You can add this at any stage. For the average concrete wall, wait until you've done a fine sanding (200 grit or higher). For low hardness surfaces, add a hardener after rough sanding (80 grit or so).

See this liquid concrete hardener on Amazon.

7. Finish Polishing

For the final sanding, use your highest-grit attachment. The higher the grit, the more polished your final wall will look.

Of course, this depends on your desired finish. If you want a more speckled finish, the goal is not to sand completely smooth. You can leave this step off.

Can You Sand Concrete With A Belt Sander?

If you only have a small area to cover, it's possible to use a belt sander, hand sander, or orbital sander. These won't be very practical for a large wall. However, they're plenty to tackle minor jobs.

Worker using a sanding machine for the uneven concrete surface

Keep in mind that this will be most effective for basic sanding. If you have major imperfections to fix, you'll probably need a special concrete grinder. The special grinding attachments make these bigger tasks more manageable.

Does Sandpaper Work On Concrete?

Regular sandpaper will work on concrete. That said, it's going to be difficult and labor-intensive.

For more effective results, use concrete-specific diamond sandpaper. Diamond sandpaper is made for masonry work. This kind of sandpaper resists wearing down against concrete.

Worker sanding the concrete wall with a sanding paper

It's essential to make sure you have the right kind as well. There is both wet and dry sandpaper. Once you determine if you'll be wet or dry sanding, be sure to pick the correct one for your project.

Additionally, grit matters. Coarse grit, such as between 40-60 grit, provides basic sanding. To remove imperfections, use a medium grit of 80-120.

If your goal is a truly smooth wall, then go even higher. The finer grit, the softer the surface becomes. For your final round of sanding, expect to go as high as 400 grit for best results.

How Much Can A Concrete Grinder Remove?

Concrete grinders mean serious business. If you have a big job ahead of you, a concrete grinder can help speed things up. They can remove as much as 1/8th of an inch at a time.

The grinding attachments and sanding grit are important as well. These factors influence just how deep you'll sand with each pass.

The next tool up is a concrete scarifier if that's not enough. However, the scarifier takes off more than just the surface. It can even cut into the underlying concrete surface.

For this reason, a scarifier should only be used by someone who knows what they're doing. It removes as much as 1/4th of an inch at a time. An untrained person can quickly find themselves in trouble with this tool.

To Conclude

Sanding the concrete wall with a big sanding paper

You can sand concrete walls for a smoother, more polished finish. For a large surface area, use a concrete surface grinder. To remove minor imperfections, you can also sand by hand.

Be sure to use diamond sandpaper, which is made for concrete. While regular sandpaper can work in tiny areas, it will wear out quickly. Diamond sandpaper is more durable and less labor-intensive.

The higher grit that you use will determine just how smooth your final wall texture is. For a coarse finish, stick with lower grit sandpaper. For a glossier wall, do multiple rounds of sanding. End with the highest grit attachment on your grinder for best results.

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