How to Clean Your Garage Floor

garage floor cleaning
CC BY Olger Fallas Painting via flickr

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.

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, there are people who 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.

deck brush for cleaning garage floorsThe 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.

cleaning garage floor
Cleaning solution of Tide and hot water

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 set 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.

Tip: Push brooms make a poor scrub brush.  The bristles are too long and the surface area is too large to apply good pressure.  Purchase a cheap deck brush with the short stiff bristles.  These work best.

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 garage floor with pressure washerConcrete is porous and can really 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 centers.  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 actually 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 a head 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.

Cleaning oil stains and grease

With the heavy cleaning done, you can now tackle the oil and grease stains that were not completely removed by the scrubbing.

Wet the stain and surrounding area first then apply your degreaser to the oil spot in full strength.  The reason for wetting first is to prevent the contaminants in the stain from spreading to a dry area.  Scrub the degreaser in and let it sit for a while.  Apply more degreaser, scrub, and then rinse with the high pressure nozzle.

Mixing a heavy concentration of Tide into something closely resembling a liquid paste works well also.  Just make sure the concrete is wet before you apply it and scrub it in.  Again, let it sit without drying out before you rinse it.  These methods will take care of most standard oil and grease spots.

If these methods don’t remove all the oil stain, there are advanced methods for removing oil stains below.

How to remove oil and grease stains from concrete

Be advised that older stains that have been in the concrete for a long time will still have some discoloration.  To make sure that you were successful in removing the oil, test it by sprinkling a few drops of water onto the surface.  It should not bead up.  If the water doesn’t soak in or beads up on the surface, then that is an indication that it was not all removed and you may have to clean it again.

Removing rust stains in concrete

There are a few ways in which to rid your garage floor of rust stains.  For small spots, the simplest is to use either lemons or white vinegar.  The white vinegar is easier to use if the spots are larger.  Squeeze the lemons or pour the white vinegar over the stain and let it sit for 5 minutes or more.  Add some more lemon juice or vinegar and then scrub with a good stiff brush.  Rinse well with water and repeat if necessary.

A high concentration of TSP mixed with boiling water works wonders on rust as well.  Be sure to let it sit on the stain for about 15 to 20 minutes before scrubbing.  Repeat if necessary.

Oxalic acid is another product that is even tougher on rust stains.  You can generally purchase it from your local home improvement center or hardware store.  Some concrete cleaners for rust stains have it as an ingredient.  It may even come in a powder form which you mix with water to make a soupy paste.

Apply the Oxalic acid to the stain and let it sit for 5 minutes before scrubbing.  Be sure to rinse real well afterwards.  Again, repeat if necessary.

Another option is to use one of the concrete rust stain remover products that are available over the counter.  You can see a whole list of some of these products here from Amazon.

For the toughest of rust stains a mild solution of muriatic acid will work wonders, but you need to be careful when using it.  We suggest a ratio of 10 parts water to 1 part acid to start.  More isn’t always better in this regard unless you are preparing your concrete for a floor coating.  If you mix it too strong right away it will etch the concrete which will make it look different from the surrounding concrete.

Safety Tip: Do not pour water into acid – pour the acid into water instead.  Pouring water directly into acid can cause it to explode in a gas that can splash back in your face.

For more instructions on how to use acid on concrete we suggest you read this post here.

Removing old paint and sealers

If you are applying a coating to your floor, you will need to remove any type of residue on the surface such as a thin filmed topical sealer, old paint, or mastic.  This needs to be done first before any attempt is made at cleaning.  There are two different methods you can use depending upon what is on the concrete.

The first would be a chemical stripper.  We highly recommend a couple of products that are available from Franmar Chemical that are environmentally friendly and very effective.  The first product is called Bean-e-doo and works great for removing mastic.  The second is Soy Gel and is very effective for the removal of old paint and urethanes.

These type of products are more expensive than solvents and take a little more time to work on the product (chemically, not physically), but are much more safe for you and the environment.  If you are cleaning the garage floor before laying down a floor covering such as roll out mats or interlocking tiles, then removal of old sealers are not necessary.

The other method is to use a floor grinder.  Special grinding heads are available for the purpose of removing mastic, paint, and sealers.  While it can be a more dusty way of dealing with old sealers and paint, it does require less elbow grease than chemical strippers.  It does cost more however.  You can read more about using floor grinders for concrete here.

Final Cleaning Tips

floor squeegee for cleaning garage floorsOne tool that can come in handy is a floor squeegee.  These work great at moving large volumes of water out of the garage and for clearing water out of low spots.  If you don’t have a squeegee an old push broom will help. You can find great prices on floor squeegees here from Amazon.

One important note to make; if you are planning on acid etching your concrete in preparation for paint or an epoxy coating, then you still must clean your garage floor as stated above.  Acid works by breaking down the surface of the concrete to expose the pores.  It will not clean away dirt or remove oil.

If you plan on grinding your garage floor then you only need to treat the oil stains.  Any other surface contaminants such as dirt and most rust stains will clean up with the grinding.

If followed correctly, you will find that these methods of cleaning a garage floor are highly effective.  It is generally thought of as the least desirable part of any floor project or garage cleaning chore, but once done it will reward you with a nice clean concrete floor that is free of dirt and stains.


Comments

  1. says

    I want to repaint my garage floor that was painted by the previous owner at least 10 years ago. He used Behr paint but I’m not sure it was epoxy. All things considered, the floor is in good condition except where the cars sit – bare spots from tire heat. I want to repaint it but do not want to go thru the mess of grinding off all the old paint. Any suggestions on what I could do? I want to use a 1 part epoxy paint.

    • Shea says

      Hi Jim. 1-Part epoxy paint will bond with regular paint so there is no need to remove the old paint that is adhered well. What you need to do is rough up the surface of the old paint with approximately 150 grit sandpaper. A pole sander works well for this or a floor maintainer with a cleaning pad will work also. This isn’t very labor intensive as you are just trying to rough up the surface, not remove it. This is required for the new paint to adhere. Once done, clean the floor real well and allow to dry properly. You are now ready to paint.

  2. Alex says

    If I am grinding for my surface prep. prior to applying my primer coat of epoxy, when should I clean and degrease? Before and after grinding or just after?

    • Shea says

      Hello Alex and good question. If you are grinding, degrease any spots that need it before you grind. Unless you have an exceptionally dirty floor, the grinding will leave you with a nice clean floor and shouldn’t need to be cleaned excessively before grinding. Any areas that you had to degrease before grinding should be checked with the water drop test afterward to make sure that it absorbs water. If you were acid etching and not grinding, then all cleaning would need to be done prior.

    • Shea says

      Hi Carol. Try mixing up a 3:1 solution of water and vinegar. Pour it on the area and scrub it good. Let it sit for 10 minutes without drying out, add some more, scrub, and then rinse well.

  3. Marissa says

    I have some cracks to fill in my garage floor. Some where the garage walls meet the floor and a few that run across the floor, essentially cutting it in half…they didn’t put expansion joints in. Should I fill these cracks before or after giving my floor a thorough cleaning, possibly using a pressure washer? And, is there a specific product you recommend for filling the cracks. Some are 1/4″ and some slightly larger. Thanks for your recommendations. This site has been a huge help so far.

  4. Brian says

    Shea,
    I have a garage floor I wanted to paint or seal and protect from oil and salt. I talked to a company which sold me on a product called densifier which is suppose to harden and seal the concrete. Well it was expensive, and was quite confident it would work, but turns out it does not seal out water, nor does it seal out oil. My problem is now to get rid of the densifier. its a sodium silicate formula, that paint wont seem to stick to, Ive elected to go with a oil based 2 part epoxy, and I need to clean the densifier off first. I have tried a metal disc floor polisher twice, acid wash, and several scrub and power wash cycles…. any Ideas ??? The company that sold me the densifier wont reply to my requests…. I paid 500 bucks for the epoxy already,, but dont want to apply it to find out it wont stick…..after all my washing Ive done, I took duct tape to see if it would stick, and no, it comes right off with no problem, no stick at all !

    • Shea says

      Hi Brian. What was the brand name of the densifier and the brand of epoxy that you purchased? There is no such thing as oil based epoxy. Is it actually an oil based concrete paint? You said nothing will stick, have you already tried applying it? Also, densifiers are inorganic which makes them non film forming. They should not interfere with a film forming coating such as epoxy. What they do is strengthen the surface of the concrete and are sometimes used before applying a film forming coating. What type of metal disc floor polisher did you use?

    • Shea says

      OK, it makes more sense. The epoxy is a 68% solids epoxy that is solvent based, not oil based. The Liquid-Hard Ultra is a lithium silicate densifier that doesn’t leave a film on the surface. Densifiers harden the surface which helps to seal the concrete, but they are not a sealer unless an additive is included, which this one does not. Both products are compatible for what you want to do. You can’t remove a densifier as it penetrates into the concrete. It will not interfere with the epoxy.

      How do you know it will not adhere? Duct tape is not an adhesion test for epoxy. Based on the stated floor prep you did you should be ready to go. Did the acid etch fizz and bubble when you applied it to the concrete? What type of metal disc did you use on the floor buffer? Does the floor have a slight gritty feel like sandpaper?

  5. Brian says

    Yes , the acid did fizz and smoke a little. not much, and no fizzle, unless it was minimal to see. I used a 20″ machine with metal disc from home depot, they had 3 different discs available, I took the least aggressive one that didn’t take much off the floor. it did knock down the high spots on the floor and didnt do much to the lower spots. I also just did a total wash down with tsp and a power washer, floor is rough and clean, I used a tuck tape test as a check to see if the tape would stick, then the epoxy should too ?
    If you think these products will adhere to each other , I feel confident to put the epoxy down, I was told by the epoxy guys to thin the first coat so it would sink in deeper, then if the second coat was needed, it could be done thicker, without thinner..

    • Shea says

      You’ve done everything and more in terms of what is required. Acid etching isn’t even necessary if you ground the floor. Based on your description of the floor, you are ready to epoxy. Yes, thinning it will allow it to penetrate a little deeper. You will need to apply another coat when you do this as the first coat will look patchy from going on thin.

  6. Brian says

    Thanx…

    Got the first coat on this morning, I like this stuff. thins out nicely and gos along way. I thinned it about 5 %. will recoat tommorrow..

    Thanx for all the help.. saved me alot of stress ! lol

  7. Lynette says

    Any suggestions for removing road salt from a garage floor? I have scrubbed and shop vacuumed it three times with a solution of 1 cup vinegar, splash of dish soap to one gallon of water followed by a good rinsing. The salt continues to resurface after a few days. My ultimate goal is to have the floor coated and am concerned about it failing do to the salt.

    • Shea says

      Hi Lynette. It sounds like you have a high buildup of salt residue in your concrete. When that happens it can require multiple washings to get it all up. You may want to use an aftermarket product such as Salt-X or Salt-Away. These are effective on concrete as well.

      Salt can lower the pH level of concrete. For a garage floor coating you want the pH leve between 6.0 – 9.0 with 7.0 being ideal. To make sure you have removed enough salt, test your final rinse water on the floor with a pH test strip. You can usually find these cheap from a pool supply store or purchase them online.

  8. Debbie Jen says

    Hi,

    I hired a contractor to polish my garage floor, the contractor used ameripolish company’s product – SURELOCK, and color is RAW SIENNA on my concrete floor. Now I am thinking about laying porcelain tile on the top of RAW SIENNA color, do I need to remove the this RAW SIENNA coating before I lay tile on the garage floor ?

    • Shea says

      Hello Debbie. Raw Sienna is a dye that was used to color the concrete as it was polished. It’s not a coating. There may have been a stain guard applied as a final treatment as well. Because the surface is so smooth due to the polishing, you would need to grind it first to roughen up the concrete surface enough to provide texture for the thinset that is used to set tile. It will most likely retain some of the color, but it will not inhibit how the thinset adheres to the concrete.

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