Learning the best way to clean a garage floor properly is a skill that is high on most home improvement lists. It is a critical aspect for any project that involves prepping a floor for paint, an epoxy coating, or for just creating a nice clean garage floor free of spills, stains, and contaminants.
Depending upon what type of garage floor project you have chosen and how dirty your floor is, there are different methods of cleaning a concrete floor that you may want to engage. We will discuss each of them as we go in order to assure a successful outcome. If your goal is to eliminate pet urine odour and stains, then we have a separate article for that here.
Cleaning your garage floor is one task that rarely makes it on your list of to-dos. However, without regular cleaning and maintenance, serious clutter and grime can build up leaving the garage in poor condition. Removing dirt, chemicals, and unwanted stains will keep your garage floor from wearing away and safe for you and your family.
How to Clean Garage Floors
Because of cars, the lawnmower tools, motorcycles and other outdoor equipment, dirt build-up and oil and grease stains are inevitable on a concrete garage floor.
Unfortunately, you are not always able to address a mess right away, or maybe you’re looking to clean oil off your concrete garage floor that’s been there for who knows how long. Unless sealed, cured concrete is not a hard, dense rock – the mixture of cement, sand, and aggregate is porous after it is mixed with water and cured. This allows stains like rust and oil to penetrate down into the surface.
To remove these stains and get your concrete clean, you need something that will also sink in and lift the offending spot. Cat litter, sawdust, baking soda, and other absorbent materials remove fresh spills but don’t do much about what sinks into the surface.
Muriatic acid is sometimes used to clean concrete garage floors. But the binder in concrete, called Portland cement, dissolves when it comes into contact with an acid. Plus, acid-based cleaners pull calcium hydroxide out of the hardened concrete, which then quickly forms a white, dusty material called efflorescence. This material can become so heavy and visible that you’ll need to clean it off of your floor.
Another cleaning agent that is widely believed to be the best way to clean a garage floor is trisodium phosphate (TSP). It is strongly alkaline, so it will not harm the concrete floor, but this also means it could cause skin irritation and even burns. TSP is also very bad for the environment. If it ends up in lakes and streams, the phosphates trigger an overgrowth of algae that results in a depletion of oxygen levels in the water, which can endanger fish and aquatic plant life.
Concrete is susceptible to dirt and stains, requiring routine maintenance.
When it comes to concrete floors, like the ones found in most garages and workshops, stains will happen. With a flat surface where you store the car, lawnmower, tools, chemicals and paint, etc., it is unavoidable that at some point, you will have to ask:
How do I clean and remove stains from my concrete floors?
It is a good question, and the answer will depend on what you want to do after cleaning. If you are going to paint or epoxy coat the floors, you will want something different than if you are going to place an interlocking rubber tile on the floor. And if you are just going to leave the bare concrete floor, you may want to remove all traces of stains from things like oil and rust.
So, as happens too often, a simple question raises a number of issues. But fear not, it can be broken down into a few easy to understand topics, and the information about concrete and how to clean it follows properly.
What is Concrete?
Concrete is a mixture of:
- Portland cement
When mixed with water, it chemically reacts (“hydrates”) and becomes the hard, man-made rock we all know.
Now, you are probably asking: why do I care about this?
You should care because it provides some of the answers on how to clean this unique material.
For example, muriatic acid is sometimes used to clean concrete and masonry. But, the binder in concrete, Portland cement, is dissolved by an acid. Dissolving the glue, holding all that sand and aggregate together is not a great idea.
Another example of the challenges one faces when cleaning a slab, when concrete hydrates, it produces calcium hydroxide as a byproduct (this is why concrete is an alkaline material). The calcium hydroxide further reacts with carbon dioxide in the atmosphere to form calcium carbonate, which is the white, dusty material you commonly see on the surface of the concrete (this is called “efflorescence”). It can become heavy enough that you may need to clean it off.
But if you use an acid-based cleaner, the acid pulls more calcium hydroxide out of the hardened concrete, which then quickly forms even more white, dusty staining. I don’t know about you, but it is reasonable to say that creating more of a stain while trying to remove it is not appealing.
While some might think of cured concrete as hard, dense rock, it is not. The mixture of cement, sand, and aggregate is porous after it is mixed with water and cures. This allows stains like rust and oil to penetrate down into the concrete. Therefore, to remove the stain, you need something that will also get into the concrete and lift the offending spot.
(Bonus nerdy fact, this porous nature is why freezing and thawing causes “spalling” of the surface, and you should never, ever use deicing salts on concrete. The salt gets into the top layer of concrete and increases the number of freeze-thaw cycles, accelerating the popping and spalling.)
All that said, it should be evident that concrete is a unique material requiring knowledge and care to properly clean and remove stains, without causing further damage.
Scrubbing The Garage Floor Clean
For the best success, the first thing you want to do is remove everything from the garage floor that is not anchored down and sweep out the heavy dirt and debris. As obvious as this seems, some people don’t want to do this, and they are the ones who always end up ruining something due to water damage.
If you have painted drywall in your garage or low electrical outlets, you may want to cover the lower 3ft by taping a few cheap plastic drop cloths to the walls to avoid water spots or shorts from electrical damage.
The easiest low budget method for cleaning the garage floor is to use a concentrated concrete degreaser, a deck brush, your garden hose with a high-pressure nozzle, and some good old fashioned elbow grease. If you don’t have a degreaser, Tide laundry detergent or TSP (Trisodium Phosphate) are excellent substitutes for cleaning concrete.
Mix the cleaning agent of choice into a large bucket of warm to hot water. For Tide, we like to use a ratio of 1/3 cup of Tide to 1 gallon of water. Follow the recommended directions for the TSP or degreaser. It is easiest if you divide your floor into sections as you clean.
Pour your warm soapy solution onto a section and start scrubbing with your deck brush. For particularly dirty floors it helps to let the solution sit for a few minutes after your initial scrubbing in order for it to work on the dirt and grime. After it has set for 5 – 10 minutes, add a little more solution and scrub again. Follow that up with a good rinsing with your high-pressure nozzle and then move on to the next section.
What’s important here is to make sure that the solution you are scrubbing with does not start to dry up before you rinse it away. The reason for this is that the contaminants in the pores of the concrete are emulsified and lifted out in the solution while it is still wet. This makes it easy to rinse out with the high-pressure nozzle. If it starts to dry out, these contaminants can be left behind with the rinsing.
Once the floor dries, you should have a nice clean surface and can inspect for any tough areas that need to be spot cleaned such as grease and oil stains.
Equipment For Cleaning A Garage Floor
Cleaning the garage floor with pressure washer concrete is porous and can become embedded with dirt and grime over the years if it hasn’t been cleaned very often or at all. If you are dealing with a floor such as this, then you do have some equipment options that can make the job easier and work great at getting the dirtiest of garage floors clean.
The first of these is a pressure washer. Pressure washers can save a lot of time in scrubbing and are excellent at cleaning concrete. Most will allow you to add a degreaser to the water for additional cleaning action. You can read more about pressure washers for garage floors here.
They are not very expensive to rent, and you can usually find them at your local home improvement or equipment rental centres. For effective cleaning, a minimum 3000 PSI washer should be used with a water flow rate of 3 gallons per minute or more.
The key to using a pressure washer is to presoak the concrete with the cleaning solution first for 10 – 15 minutes. Work in sections, as stated above. Once the area has soaked, add more water to the floor and use the pressure washer to start rinsing the grime away.
The yellow 15-degree fan tips work best for dirty concrete. For particularly stubborn areas such as stains, you can use the more powerful turbo tip. Just be careful not to linger too long in one area when using a good pressure washer and keep the tip moving. Because the water action is so abrasive, you can etch the surface of the concrete if you are not careful.
The second equipment option you can use is a floor buffer (also known as floor maintainers) with a nylon scrubbing head for concrete. You can rent these inexpensively as well. Be sure to tell the rental company that you will need ahead for cleaning concrete. Home Depot is a great resource for these.
Garage cleaning brush for floor maintainerWhen using a floor buffer you will clean the concrete in the same manner as if using a deck brush. Just substitute the floor buffer for the deck brush. Take your time as you go and let the buffing machine do its work. You may have to add a little water as you scrub to keep the solution wet and foamy.
These can do wonders to some concrete with the floors turning many shades lighter after scrubbing with a floor buffer.
How to Remove Oil and Grease Stains from Concrete Garage Floors
Occasional oil or grease stains are inevitable in a garage. Cars, lawnmowers, and other outdoor power equipment may leak fluids. You may also spill a drop or two of oil when working with tools. It’s best to try and clean these spills right away to avoid slipping on fresh oil, tracking it into the house, or leaving a stubborn stain.
To clean a fresh spill, sprinkle cat litter or sawdust on oil or grease to absorb the liquid. Leave the litter or sawdust on the spill for about a day, then sweep it up and dispose of it properly.
Once you’re done sweeping, pour dry dish soap or laundry detergent onto the stain. Let it sit for 45 minutes. Next pour water on the area and scrub with a nylon-bristle brush, which will not scratch the surface of the concrete. Allow the soap to sit for 10-15 minutes and scrub again. After scrubbing, rinse with a power jet wand, diluting and directing the soapy water out of the garage.
Older stains are more difficult to remove. You can repeat the cleaning process several times, or buy a de-greasing product at a home- or builder’ s-supply store. Even with these products, you may need to apply them and scrub several times to remove stubborn stains.
How to Remove Rust Stains from Concrete Garage Floors
Rust stains leave a telltale mark on concrete garage floors. Tools like screwdrivers, hammers or nails, will leave rusty spots if they sit too long on the garage floor, especially if they get wet. Wheel hubs, garden tools or metal buckets can also leave rust stains.
To remove these stubborn marks, squeeze a lemon or pour white vinegar on the stain and allow the liquid to sit for 10 minutes or so. Then scrub with a nylon-bristle brush and rinse the area with water. You may need to repeat the process several times for stubborn rust stains.
Another option is to make a thick paste using a laundry detergent that contains baking soda. Mix water and detergent and leave it on the rust stain for an hour. Be sure to continually keep the paste wet otherwise it will harden and become ineffective. Finally, scrub with a nylon-bristle brush and rinse with a hose.
How to Remove Paint from Concrete Garage Floors
Paint stains can be hard to remove. However, with a few simple steps, you should be able to get rid of them. First, use a putty knife to scrape off loose paint, then sweep the area around the stain.
Mix a solution of TSP and water, follow directions on the label and wear a glove. Pour the solution on the stain and scrub it into the remaining paint. Rinse with water. Next, scrape any remaining bits of paint off the concrete floor and rinse again.
For tough paint stains, you may need a commercial paint stripper. This solution should stay on the stain for several hours before scraping or scrubbing the concrete. Wear gloves and make sure the garage is well ventilated.
Homemade Concrete Cleaning Solution
For regular cleaning, a solution of baking soda and water will loosen dirt and grease and help keep your garage floor clean. Mix a half-cup baking soda in a gallon of warm water and use it as an all-purpose cleaner.
You can also mix baking soda with a few drops of liquid soap, to make a paste, and use it to scrub light stains.
Don’t underestimate the power of warm, soapy water to keep your floors clean and remove minor stains. Mix about one-third cup powdered laundry detergent in a gallon of warm water, and scrub with a nylon-bristle brush. After cleaning your garage floor, always rinse with your power jet wand. The power jet wand is perfect for this job because the powerful stream will make rinsing quick and easy.
A garage is a hard-working room and spills are bound to occur. Put a little muscle into existing stains to clean them up, and take care of new spills without delay. Doing it a bit at a time makes it easy to keep your concrete garage floor clean.
Keep Your Garage Floor Cleaner, Longer
You can extend the life of your cleaning job by doing a little preventive maintenance here and there. Don’t allow anything metal to sit directly on the concrete where it may leave rust spots, and if you drip any oil put some cat litter on it immediately to soak it up. Consider putting down a mat to park your vehicle over, and be sure to sweep out dust and leaves before they have a chance to accumulate.
Sealing Your Garage Floor
Now that you have a pristine garage floor, you may want to consider sealing or painting it. This will increase the stain-resistant qualities of the surface and make it easier in the future to clean up dirt and oil. You can purchase concrete floor sealant in the colour of your choosing, and even use decorative flakes.
You’ll roll on the coating with a brush, and avoid walking on it for a couple of days and driving on it for a week. Not only will your garage floor look like brand new, but it’ll also be easier to clean in the future.
Now that your garage floor is freshly washed, you can either let it air dry or mop it up with towels. As you put your things back inside, this is the perfect time to do a little spring cleaning and ensure that you’re not putting any dirty, broken or rarely-used items away. By staying on top of the cleanliness of your garage, you’ll save yourself a lot of elbow grease over time.