How to Polish Concrete Floors

polishing concrete floor with floor polishing machine — Photo:
elenaleonova / Getty Images

Working Time: 12 hours
Total Time: 3 days
Skill Level: Intermediate
Estimated Cost: $800 to $1,200

Polishing concrete floors is an effective way to achieve a finished look. Whether you're sprucing up old concrete in your garage or putting a finishing touch on a newly poured concrete pad, polishing gives concrete floors a smooth, lustrous look and feel. Polishing concrete isn't complicated, but it requires tools you probably don't have lying around the house. Here, we've broken down exactly what it takes to polish concrete floors yourself, including the items you need to get the job done.

Before You Begin

The key to a beautifully polished concrete floor is proper prep work. Here are some things you need to do before polishing a concrete floor.

Thoroughly vacuum the surface. Use a shop vac to remove every bit of dust and debris that you can.
Wash the concrete. Mop the floor using mild concrete soap and water to remove any remaining dust and debris.
Let the concrete dry. Before moving to the next prep steps or polishing, make sure the concrete is fully dry.
Fill the cracks. Patch any holes or cracks using concrete crack filler, following the manufacturer's instructions for proper application.
Determine the hardness of the concrete. To do this, you need a concrete scratch test kit. Follow the manufacturer's instructions to conduct the scratch test, which helps you choose the right level of grit for polishing the concrete floor.
Rent a walk-behind diamond grinder and grinding discs. Concrete polishing machines are expensive, so you should rent one. Shop your local tool rental stores. They should have both grinders and compatible diamond grinding discs. Additionally, they can offer guidance about the grinding discs you should use based on your concrete's hardness.

Patience is key when polishing new concrete. Newly poured concrete pads can take a month or more to fully cure and be ready for polishing.

What You'll Need

Equipment / Tools

Shop vac
Mop
Walk-behind concrete grinder with grinding discs
Roller frame and extension pole
Protective gear, including safety goggles and respirator or mask

Materials

Concrete scratch test kit
Mild concrete soap
Concrete crack filler
Concrete sealer
Microfiber mop heads
Concrete sealer roller

Instructions

How to Polish Concrete Floors

These steps are general guidance for polishing a concrete floor using a walk-behind concrete grinder. If these instructions differ from those provided by the concrete grinder's manufacturer, default to the manufacturer's instructions.

Set Up Your Concrete Grinder

Put on protective gear before beginning the project. Set up the concrete grinder according to the manufacturer's instructions or the setup instructions provided by the tool rental store. The setup usually includes attaching a water hose or dust extractor and installing the appropriate grinding disc based on the hardness of the concrete.

The machine determines whether your concrete grinder utilizes water or dust extraction to control dust. Never grind concrete without water or a dust extractor in place. Not only will the concrete dust create a mess, but it is dangerous to breathe in.
Begin Polishing

Move the machine to a corner or hidden area so you can start it and practice before moving to the more visible concrete. Engage the machine and begin the polishing process.
Move the Machine Slowly and Steadily

Push the machine in slow, straight lines, using controlled movements rather than moving in a random pattern. This encourages even grinding and lets you better track which area has been polished and which hasn't.
Progress Through Finer Grits

After evenly grinding the initial layer, progress through finer grinding discs to achieve a smooth, polished surface.

Some concrete grinding professionals recommend applying a concrete densifier between the initial grinding phase and the polishing phase. Consult a professional or the tool rental store for recommendations.
Clean the Floor

Clean up any remaining concrete dust using a microfiber mop.
Seal the Polished Concrete

Once the floor is clean, follow the manufacturer's instructions on the concrete sealer to seal the freshly polished concrete. The process usually consists of rolling the sealer on the concrete, letting it dry, and then applying one or more additional coats.

When to Call a Professional

Concrete can differ significantly from surface to surface, meaning no two surfaces should be polished or sealed in the same way. While it's possible to achieve great results by renting a machine and polishing a concrete floor yourself, it's not guaranteed. When in doubt, consult a concrete professional regarding which machine and grinding discs to use and which products, such as concrete sealants, to use.

A professional will undoubtedly achieve a quicker, better polished concrete floor than a DIYer. However, it's a good idea to get a professional quote and compare this price with the total cost of the grinder rental and purchase of grinding discs before proceeding.

Tips for Maintaining a Polished Concrete Floor

Follow these tips to maintain your newly polished concrete floor's smooth feel and shiny surface:

Keep it clean. Like any floor, a polished concrete floor requires frequent cleaning. Dust and debris left on the surface can scratch it when walked on.
Wipe up spills immediately. Even a sealed concrete floor can stain, so it's best to wipe up spills promptly.

Avoid harsh cleaning products. Abrasive cleaners and acidic or alkaline cleaning products can damage the smooth surface of the polished concrete. Instead, clean your concrete floors using microfiber mops and cleaning agents with a neutral pH.
Reseal as needed. Reseal the concrete as specified by the sealant's label. Depending on the type of concrete sealant you use, it could last one, two, or even five years between resealing coats. As with a wood sealant, it's easier to reseal concrete before the surface is compromised.