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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.  As simple as it sounds, many a homeowner has had a disappointing experience with a floor coating due to a poorly cleaned floor.

Depending upon what type of floor project you have chosen and how dirty your floor is, there are different methods of cleaning that you may want to engage.  You may have a brand new home with a fresh floor to start with or an older home with an abundance of grease and grime that needs to be removed.  Whichever the case may be, learning how to clean your garage floor properly will help to insure a successful floor coating.

Removing old paint and sealers

The first thing that needs to be done if you are applying a coating to your floor is to determine if you have any type of residue on the surface such as a thin filmed topical sealer, old paint or mastic.  If you do, then this has to be removed first and the best way to do it is to use 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.  They 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.

Cleaning oil stains

The next item that needs to be addressed are any oil stains in the concrete.  Many times a small oil stain can be cleaned with a concrete degreaser.  For larger spills, treating it first with kitty litter, which is a natural poultice, will help to pull some of the oil out.  Scrub it first with a degreaser to emulsify the oils in the concrete then apply the kitty litter onto the degreaser before it dries.  Grind it in real good with the heal of your shoe and then let it sit overnight. Sweep it up the next day and the oil should be gone.  Click here to learn more about removing oil stains.

Removing Rust Stains

There are a few ways in which to rid your garage floor of rust stains.  The simplest is to use either lemons or white vinegar.  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.

Oxalic acid is another product that is even tougher on rust stains.  You can purchase it from you 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 acid to the stain and let it sit for 5 minutes before scrubbing.  Be sure to rinse real well afterwards.  If you are going to acid etch your garage floor in preparation for a coating, then the acid will remove any rust on the concrete and you won’t need to clean the stain separately unless it is unusually large in area or has been set-in for a long period of time.

Equipment for cleaning a garage floor

With the oil spots removed, it’s time to start cleaning the entire floor.  Concrete is very porous which allows it to easily collect dirt and grime.  Just hosing out the garage with a little soap and water won’t do the trick.  We need to get that grime out of the pores as well as off the immediate surface.  Two items that are great for this are pressure washers and floor buffing machines.  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 cleaning.  Make sure to rinse afterward for a nice clean floor.  A minimum 2700 PSI washer should be used.

If a pressure washer is not an option, then a standard floor buffer with a stiff nylon brush attachment made for concrete will work just as well.  Either one of these can be rented at your local tool rental or home improvement center.  If neither of these are available, then a good long handled scrubbing brush with stiff short bristles is very effective, just more labor intensive.  Push brooms are not good because the surface area is too large to apply enough pressure per square inch for scrubbing and the long bristles move around too much.  If not using a pressure washer, make sure you have a high pressure nozzle for your hose to lift out the dirt and grime when you rinse.

Scrubbing the floor

If you don’t have a degreaser, then for standard cleaning 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 I like to use 1/3 of a cup 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 solution onto a section and start scrubbing with your floor buffer or scrub brush.  For particularly dirty floors it may be good 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, 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.

scrubbing garage floorWhat is important here is to make sure that the solution you are scrubbing with does not start to dry before you rinse it away.  On particularly warm and dry days this can happen fairly easily if you aren’t careful.  The contaminants in the concrete are lifted and emulsify in the solution while it is still wet, making it easy to lift out of the pores of the concrete when you rinse.  If it starts to dry these contaminants can be left behind.  If you are using a floor buffer you may need to add a little water to the floor while scrubbing to keep the solution wet and foamy.

Once the floor dries you should have a nice clean surface.  To make sure that you rinsed well enough, apply a strip of painter’s tape to the floor and then pull it up.  If it comes up clean, then mission accomplished.  If it has bits of dry powdery debris attached to the tape, then the rinse wasn’t good enough and you will have to do it again.

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 on the surface.  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.  You can do this test after grinding or acid etching the floor if you like.

One important note to make; if you are planning on acid etching your concrete in preparation for paint or an epoxy coating, then you 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 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 rust stains will clean up with the grinding.

If followed correctly, you will find that this process of how to clean a garage floor is highly effective.  It is generally thought of as the least desirable part of any floor project, but once done it will reward you with a nice clean surface for your coating of choice.

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