How to Sand Concrete

There’s a rising trend in the construction industry where homeowners prefer sanded floors due to their attractiveness and practicability. Sanding concrete might be a good option if you desire a more finished look on your concrete floors or countertops.

Naturally, this leaves the question, how do you sand concrete? This article will discuss how to sand concrete and the benefits of smoothing concrete.

Can you sand concrete?

You can sand concrete to achieve a more refined concrete surface. If you use the proper tools and procedures, sanding concrete can be relatively straightforward.

There are different methods of sanding concrete. It can be through either a wet or dry process, influencing the kind of sandpaper you will use.

When sanding, you also need to consider the kind of finish you want to obtain. For instance, smooth finishes are suitable for countertops, and you mainly achieve it through hand sanding.

For a speckled finish, you will have to remove about 1/16th of an inch from the concrete’s surface to create an aggregate finish.

Why should you sand concrete?

Concrete is the most commonly used material for construction and is well adapted for interior and exterior finishes. There are several reasons for sanding concrete, and we will look at the main ones below:

Finish

Sanding concrete is ideal for finishes. For homeowners, aesthetics are the main reason behind smoothing concrete. You might want polished concrete floors, kitchen countertops, or walls.

For instance, the salt and pepper finish needs some extra work. To achieve this finish, you need to remove 1/16th of an inch from the layer of concrete. The main goal is to remove concrete to leave a salt and pepper look resembling polished granite. 

Round edges 

Concrete is hard and, in most cases, wear-resistant. After concrete curing, some imperfections such as sharp edges, spots, and protrusions might remain in the concrete. 

To minimize accidents or injuries, you need to sand the concrete to remove the bumps and imperfections. Sanding the protruding edges also enhances the surface’s overall appearance.

Remove imperfections

Sometimes you might have hard-to-remove imperfections such as paint coatings and stains. Some stains are easy to remove, but others are resistant even to the most potent chemicals available. You can remove the affected layer of the concrete surface, which will restore the original appearance of the concrete.

Repairs

If there’s a crack in a concrete surface that needs repairs, you will need to sand the concrete surface to achieve a consistent look after the repairs. If you repair the concrete using sand fillers, and the color of the fill differs from the original concrete surface, you might want to apply paint after the sanding.

Concrete finishes

Pouring the concrete is the first step of your project, but you need to pick the right finish to complete your project successfully. Concrete finishes improve aesthetics and safety and can increase the durability of a concrete surface.

Below are a few options of concrete finishes that look and serve you well.

Smooth finish

This is the most effortless finish to achieve as all you need is light sanding by hand or polishing the concrete surface using an orbital sander. You do not remove much of the concrete surface in this finish, as you only polish the top layer to achieve a smoother and shinier surface.

Salt and pepper finish

Concrete achieves a salt and pepper finish by exposing the fine aggregate. The tiny exposed pieces of stone and sand look like salt and pepper. The speckled surface gives a unique impression different from a semi-exposed or fully exposed aggregate surface.

This concrete finish also easily blends in with almost any structural design. The top layer of the concrete is sanded off without revealing any coarse aggregate to achieve a salt and pepper finish. This gives a subtly rough and decorative concrete surface texture. 

Exposed aggregate finish

The main idea behind an exposed aggregate finish is to have a level concrete surface with aggregates distributed evenly and air voids kept at a minimum.

The types of aggregates in this finish are chosen for their appearance. They might be colored glass, granite, attractive stones, or other sturdy materials.

This finish is tough to achieve but not impossible. To expose the aggregate, you might need to remove close to a quarter-inch of the concrete. Therefore, you will need specialized equipment such as a powered polisher or sander to cut through the concrete surface.

This finish is ideal for garage floors and driveways, as it provides more traction than ordinary surfaces.

Concrete sanding tools 

It is easier to sand concrete when working with specific concrete sanding tools. The tools you use depend on your project’s size and the type of concrete you are working on. Concrete sanding tools have their respective strengths and weaknesses, which you will need to know before choosing a specific tool for use. 

Below is an overview of some of the available concrete sanding tools.

Concrete grinding wheel

A concrete grinding wheel helps you sand concrete if you have a small working area or a specific spot that needs grinding. The concrete grinding wheel is ideal for wet and dry sanding. It has air holes that help cool the wheel while working and increase its lifespan.

Handheld concrete sander

Handheld concrete sanders are also known as edge grinders, and the user holds them during sanding. They are ideal for small areas such as walls and countertops.

Handheld sanders have variable speed options and an integrated water supply that makes it easy to facilitate the wet sanding of concrete surfaces. The small size allows you to have better control over concrete edges.

However, it would help to consider using vacuum and hose attachments on this sander as the sanding creates a lot of concrete dust you shouldn’t breathe in.

The convenience of handheld sanders makes them easy to use on horizontal surfaces, but it can be more challenging to work on walls.

Belt sander

A belt sander has a loop of sandpaper attached to an electric motor and two drums. This powerful sanding machine rotates at high speed and is used to quickly sand large amounts of concrete. In addition, most belt sanders come with a vacuum system that helps to clear up all the dust produced.

Belt sanders have two options; a stationary sander, best for removing dust materials, and a handheld sander, which works best on immobile surfaces. A belt sander is easy to use and is ideal for standard large projects that require a ton of work.

Although great for aggressive projects, a handheld belt sander must be suitable for large surfaces like garage floors and may sometimes leave sanding marks behind. To avoid this, one has to use the right loop of sandpaper. Small-size sandpaper is best used to sand smaller surface areas, while larger projects use large loops for the perfect sanding.

Orbital sander 

An orbital sander is a handheld sander that sands concrete in a random circular motion. Compared to a belt sander that uses forward and backward movement, an orbital sander can move in any direction, making it suitable for sanding concrete bathroom floors and countertops. In addition, this feature makes it easier to use as it offers a variety of movements. 

The small orbits in an orbital sander move in circles and help quicken the sanding process. This machine has sandpaper attached and is suitable for small surface jobs, smoothening, and final touches. Orbital sanders have a passive dust collection system, producing a lot of dust when used. 

Floor Concrete Grinder

Floor concrete grinders are large machines with wheels mainly used on larger concrete surfaces like large patios. It has a motor that rotates the polishing pad smoothening the concrete floor and making it slip-resistant. This feature ensures safety as you can easily use the concrete floor even when the surface is wet.

The types of floor concrete grinders are; edge grinders, corner grinders, diamond grinders, oscillating floor machines, roller track grinders, tie and stone floor grinders, and marble floor grinders. 

Angle Grinder

The unique features of an angle grinder are its circular grinding blade, a side handle, and a motor system that sands concrete properly.

Unlike traditional sanders that use sandpaper, angle grinders have powerful hard discs that sand concrete faster. You should be careful when using angle grinders to avoid inconsistent concrete sanding.

Walk-behind concrete sander

The walk-behind sander has an adjustable handle that allows one to polish or sand a floor while walking behind it. You can use smaller versions of the walk-behind sander for sanding walls, but it needs a lot of skill to familiarize yourself with how to control the machine.

The walk-behind sander is best when sanding large surfaces such as outdoor surfaces. However, it would be best to be consistent with how much you sand in every spot to achieve a uniform and consistent look. You can also attach walk-behind sanders directly to a vacuum or hose to reduce the dust as you sand the concrete surface.

Polishing pads

Suppose you do not have access to electric or power tools for polishing concrete, or you only need to polish a tiny concrete surface. In that case, you might consider doing the work manually using polishing pads.

Regular sandpaper is not solid or durable enough to polish a concrete surface, and that’s why you need a polishing pad or diamond sandpaper.

Manual sanding is similar to using a power tool, though tiring and less efficient. When sanding manually, you also need to mitigate the dust produced. You can keep your work area wet and wear a face mask to avoid inhaling the dust. Polish the surface in long strokes and apply uniform pressure to prevent unevenness of the polished surface.

In manual sanding, you need sandpaper with the correct grit to cater to your project needs. The sandpaper also depends on the type of concrete polishing you are doing. Your sandpaper needs to be compatible with wet environments for wet concrete sanding. Start with coarse sandpaper and move up to smooth sandpaper to achieve a smooth finish.

How to sand concrete

To achieve a perfect finish and a smooth concrete surface, you must follow the proper concrete sanding process. Below is a step-by-step guide on how to sand a concrete surface.

1. Prepare the surface

The first step is to inspect the surface and prep it before polishing. Remove any bumps by chiseling, remove dust and debris, and fill up any holes on your concrete surface.

2. Divide your working area

If you are working on a large area, divide it into separate zones and work on attaining a uniform finish in each zone instead of a consistent finish on the entire region.

3. Use the orbital sander

Connect your water hose to the sander and apply pressure to the surface to get a uniform finish. Ensure you keep the sander level and use a constant water supply. You can also perform the sanding manually though it may take longer and not produce the desired results.

4. Clean the surface

After the first sanding pass, you can clean the surface by vacuuming or using a sponge.

5. Repeat the process

If you have not achieved the desired results, use finer-grade sandpaper till you achieve the desired results.

6. Protect the surface with a finish product

After sanding, allow your concrete surface to dry. After drying, you then need to apply a finish product such as concrete sealant to protect the concrete surface from wear and tear. The sealant also protects the surface from spills and stains.

Taking care of sanded concrete

One must take care of polished concrete to avoid constant sanding while maintaining its shine.

Some of the ways you can take care of sanded concrete are;

• Cleaning any liquid spills and stains quickly before they dry up or get absorbed to the surface. 
•  When utilizing a mop and bucket, ensure that the water and mop are clean. For larger areas, use the nonabrasive pad of an automatic floor scrubber to clean the concrete properly.
• To completely remove dirt while cleaning, combine water with a neutral floor cleaner that will not ruin the concrete floor.
• After applying the cleaner, give it time to work efficiently before mopping or vacuuming the surface clean.
• To prevent your concrete floor from wearing out, clean an area portion by portion to prevent the cleaning solution from drying up on the concrete.

FAQs

Summary

Concrete sanding is a common practice in modern construction projects. It gives surfaces a smooth, aesthetic finish. 

If you need to sand a concrete surface, following the reference guidelines in this article will give you the best results. However, it is best to have your concrete surface sanded by a professional.